Sehrou Guirassy netted a second-half penalty to earn FC Koln a 1-0 win against Arsenal and inflict a first Europa League defeat on the Premier League side.
After wasting a few promising first-half opportunities, the best of which saw Francis Coquelin hit the post, the Gunners were made to pay by their out-of-form opponents.
Guirassy stepped up after being brought down by Mathieu Debuchy inside the box to blast home the spot kick, keeping his side in last-32 contention in the process.
Relive how the 90 minutes of action unfolded with Sports Mole's live text coverage below.
5.00pmHello and welcome to Sports Mole's live text coverage of the Europa League group-stage tie between FC Koln and Arsenal at the RheinEnergieStadion. The hosts need all three points tonight if they are to stay in last-32 contention heading into the final round of fixtures, while anything other than defeat for the already-qualified Gunners will see them through to the knockout stages as Group H winners.
5.02pmNo real pressure on the Gunners this evening, then, as they know that they will contest European football post-Christmas regardless of results against Koln and BATE Borisov over the next fortnight. That said, Arsene Wenger knows all about the importance of momentum, which is particularly important at this time of the year with the fixtures coming thick and fast - 13 between now and January 3, in fact!
5.04pmARSENAL TEAM NEWS!
STARTING XI: Ospina; Chambers, Mertesacker, Holding; Debuchy, Coquelin, Elneny, Maitland-Niles; Wilshere, Welbeck, Giroud
SUBS: Macey, Sheaf, Willock, Iwobi, Nelson, Akpom, Nketiah
5.06pmAs expected, Wenger has made wholesale changes to his starting lineup for this trip to Germany. The big news is that Danny Welbeck leads the line for the Gunners this evening, as he makes his latest return from injury. Wenger has talked up the forward's chances of making England's squad ahead of next summer's World Cup finals, but the only way he will achieve that is by staying fit between now and May.
5.08pmWenger has actually made 11 changes in all, with Francis Coquelin - a second-half sub in the 2-0 win over Tottenham Hotspur - among those to come into the side. Mohamed Elneny will start alongside him in midfield, while Jack Wilshere is handed a more advanced role alongside Welbeck and Olivier Giroud in what appears to be a 3-5-3 formation. Should that be the case, Callum Chambers and Ainsley Maitland-Niles will take up wing-back berths.
5.10pmMaitland-Niles is a bit of a European expert now, having featured down the left flank in all four of Arsenal's previous matches in this year's competition, although it remains to be seen how Chambers will perform in that position on his first Euro outing. Giroud had been nursing a thigh strain in the build-up to tonight's match, incidentally, but he has recovered in time to start, while Theo Walcott - suffering from illness - misses out on the squad entirely.
5.12pmFC KOLN TEAM NEWS!
STARTING XI: T.Horn, Sorensen, Maroh, Mere, Klunter, Ozcan, Jojic, J.Horn, Cordoba, Guirassy, Osako
SUBS: Kessler, Olkowski, Risa, Lehmann, Rausch, Nartey, Bisseck
5.14pmSwitching attention to the home team, manager Peter Stoger has reverted to a three-man defence to essentially match Arsenal's 3-5-3 formation. Jorge Mere starts on the left of the defensive trio, alongside Dominic Maroh and Frederik Sorensen, while Jannes-Kilian Horn replaces Konstantin Rausch at left wing-back. On the opposite flank, German youngster Lukas Klunter is given the nod up against Maitland-Niles.
5.16pmMatthias Lehmann misses out on a place in the starting XI, meanwhile, and Stoger has opted to go with Yuya Osako, Jhon Cordoba and Sehrou Guirassy in an attack-minded side. This is a Koln side minus as many as seven first-team players due to injury, with Jonas Hector, Marcel Risse and Domenique Heintz among those to miss out. Marco Hoger and Christian Clemens, former teammates of Sead Kolasinac at Schalke 04, are also absent.
5.18pmTo make matters worse for the Billy Goats, they lost Simon Zoller to injury in their 1-0 defeat to Mainz last time out and will likely be without him until the New Year. Leonardo Bittencourt made a timely return in the same match, although he is not risked tonight. Stoger's hand has very much been forced for this big Group H match, then, as he opts for an attack-minded XI to pick up the three points required.
5.20pmVery little experience for Arsene Wenger to call upon from the bench, with his back-up players making a combined 21 European appearances between them. Among the subs is young forward Eddie Nketiah, who rescued Arsenal with a couple of goals against Norwich City almost a month ago to the day, while fellow youngsters Reiss Nelson and Joe Willock - impressive when called upon in recent months - are also in the matchday squad.
5.22pmThe hosts head into this match knowing that three points are a must if they are to overhaul BATE Borisov and Red Star Belgrade to finish second in Group H, with just two rounds of fixtures left to play. The Billy Goats managed to keep their European campaign just about alive with a 5-2 win over the Belarussian side a few weeks ago; five different players registering in that one to get their season up and running.
5.24pmKoln lost three Europa League matches on the spin before that big-scoring win over BATE, scoring once and conceding five in the process. The highlight of their season arguably came in the opening Group H contest when scoring early on against Arsenal at the Emirates Stadium, where they were backed by a good 10,000 of their supporters, before inevitably crumbling and losing 3-1 to three second-half goals.
5.26pmJhon Cordoba, since linked with a move to a couple of English clubs, opened the scoring in North London with a superb long-range drive, but Sead Kolasinac, Alexis Sanchez and Hector Bellerin responded for the Gunners to set the tone for both sides' campaigns. If the Billy Goats lose tonight - which is the result the bookmakers are heavily backing - and one of BATE or Red Star win in Belarus, they will be confirmed out before their final-game trip to Belgrade.
5.28pmStoger will be praying for all three points this evening, however, to prolong his side's campaign by at least another two weeks, potentially setting up a final-game shootout with Red Star Belgrade in Serbia on the same night that Arsenal play host to BATE Borisov. The omens are not good for the German outfit, though, as they have won just two of their 13 previous meetings with English opposition, with both of those triumphs coming on home soil.
5.30pmAmong those previous defeats to English sides was a 2-1 reverse at the hands of Nottingham Forest in the second leg of the 1978-79 European Cup semi-finals. That was then, though, and they have since spent a long time away from the continent, with their 5-2 win over BATE earlier this month ending a run of four Euro defeats - three coming in this campaign and one in the 1997 Intertoto Cup.
5.32pmKoln had spent 20 years away from European football prior to qualifying this time around, last dining at the top table when finishing runners-up to Real Madrid in the UEFA Cup. Stoger deserves plenty of praise for guiding them back among the elite, albeit temporarily, and the man in charge certainly boasts plenty of experience as he has won four league titles - the most recent with Austria Vienna in 2013.
5.34pmStoger comes up against a man who certainly knows all about success down the years, as Wenger has won three league titles and seven FA Cups during his 21-year reign at Arsenal. The Frenchman's best-ever finish in Europe came in 2006 when finishing runners-up to Barcelona in the Champions League, but he will be hoping to go one better this time around in UEFA's secondary competition.
5.36pmThe Europa League is offering Koln a welcome distraction from their domestic woes, having failed to win any of their opening 12 Bundesliga matches - a truly shocking return. Ten of those games have ended in defeat, leaving them bottom of the standings with a goal difference of -19 and surely on their way to relegation. It is in stark contrast to their form of last season, when putting together a good run of form to finish in fifth place.
5.38pmPREVIOUS MEETINGS!
The reverse fixture in September marked the first time that these two sides have faced off in European competition; Arsenal recording a 3-1 victory in North London after recovering from Jhon Cordoba's superb early strike. The Gunners' record against German opposition reads 17 won, six drawn and 14 lost in 37 matches, with eight of those defeats coming away from home.
5.40pmArsenal have lost on each of their last three visits to Germany, in fact, scoring two goals and conceding 12 goals in the process - Bayern Munich had a lot to do with that! Far less stress for the Gunners on this latest venture overseas, though, as they are already into the last 32 thanks to a record of three wins and one draw from their opening four Group H fixtures.
5.42pmThe 0-0 draw with Red Star may have been uninspiring, yet it was a case of job done as far as Wenger was concerned as his side achieved their target of making it out of the group phase with minimal stress. Arsenal had previously seen off the Serbian club with a 1-0 away win, courtesy of a fine Olivier Giroud goal, and they also scored seven goals en route to defeating Koln and BATE.
5.44pmA point in these remaining two fixtures against Koln (a) and BATE (h) will see Arsenal through as Group H winners, which is all the more important in this competition as the Champions League dropouts will enter post-Christmas. The Gunners also remain alive in the EFL Cup - just, as they required a late Eddie Nketiah goal to rescue extra time, and then another goal from the young striker to win the contest in the additional 30 minutes.
5.46pmLast weekend's 2-0 win over Spurs further lifted spirits around the Emirates Stadium, leaving Arsenal in sixth place in what is a congested table at the top end - albeit with Man City seemingly running away with the title. Two other teams find themselves on 22 points alongside Arsenal, including next weekend's opponents Burnley, setting up what should be an entertaining clash at Turf Moor on Sunday afternoon.
5.48pmArsenal have recovered from their 3-1 loss at the hands of Man City to climb to within a point of the top four, but the Citizens are 12 points better off so the title is once again out of the question. All focus is on European action tonight, however, in what is the Gunners' first taste of the Europa League group stage. They last participated in UEFA's secondary competition in 1999-00, when losing to Galatasaray in the final on penalties.
5.50pmWenger's charges have lost just two of their last 15 matches in all competitions, meanwhile - against Watford and Man City - and now face a run of 13 fixtures between tonight and January 3, taking in games against Manchester United, Liverpool and Chelsea. All three of those matches are at the Emirates Stadium, while West Ham United also visit in the quarter-finals of the EFL Cup just before Christmas.
5.52pmDID YOU KNOW?
Three-times Premier League champions Arsenal have not lost any of their last nine UEFA Cup/ Europa League matches, excluding penalties, since a 2-1 defeat to Deportivo La Coruna in the 1999-00 campaign. The Gunners have won all four away matches since that slender loss in Galicia 18 years ago.
5.54pmWenger does not have the greatest of records on the continent, truth be told, but dropping down to the Europa League this season does at least provide him with a chance to taste some success. Much like domestic rivals Manchester United last term, winning this secondary competition can provide a major boost and act as a springboard for further silverware. Part one is already complete, as they have cruised through the group phase.
5.56pmMANAGERS' COMMENTS!
Peter Stoger: "The players that we have in their respective positions will pretty much have to take on both matches completely. We do not have a large selection right now. It is certainly a large challenge, but we want to use the opportunity we have to remain in this competition. We are still in it."
Arsene Wenger: "[Welbeck] has the potential to go and if he's fit he will go, I'm convinced of that. It is a big year for him, but I want it to be a big year for him and for Arsenal too. As a consequence of that, the best way to go to the World Cup is not to think 'I have to prepare for the World Cup', it is to do well for your club and automatically you are in the national team."
5.58pmBoth sets of players have now made their way on to the field of play, with kickoff at the RheinEnergieStadion just a couple of minutes away. Arsenal, showing a full 11 changes from their win over Tottenham Hotspur five days ago, require just a point to make it through as Group H winners; FC Koln need all three points if they are to keep their last-32 hopes alive.
1 minKICKOFF! Arsenal get us up and running at a packed RheinEnergieStadion. FC Koln may be completely out of form domestically, but their fans - among the best in German football - are getting right behind them this evening.
3 minSAVE! The visitors being given the chance to knock the ball around at the back and into midfield early on, as Koln sit back a little. A promising early move ends with Maitland-Niles shooting goalwards for Timo Horn to keep the ball out.
5 minAs mentioned in the build-up to kickoff, Koln have gone with a three-man backline this evening - the same formation that served them well en route to finishing five in the Bundesliga last season. Arsenal also line up in a 3-5-3 system.
7 minMertesacker remains composed to knock the ball back to David Ospina, who has been given the nod over Matt Macey tonight. The experienced German defender last featured in the 2-1 win over Swansea City - his sixth outing of the campaign.
9 minSAVE! Jhon Cordoba, the scorer of an impressive goal in the reverse fixture, finds some space to get a shot away. David Ospina did well to keep the ball out, with Koln unable to then capitalise from the resulting corner kick.
11 minA couple of early attempts, then, with Maitland-Niles and Cordoba forcing saves out of Horn and Ospina respectively. Not a great deal between the sides so far, but it is Arsenal who have seen more of the ball in advanced positions.
13 minCoquelin has twice miscontrolled the ball, allowing it to run out of play on both occasions. The hosts looking lively over the last couple of minutes, without managing to get the ball into the 18-yard box for Cordoba to get on the end of.
15 minGiroud is unable to trap the ball when it is played into his path. Not seen a great deal of the Gunners' forward players in the opening 15 minutes of the contest, with Koln now the team on top and enjoying more of the ball.
17 minPoor from Cordoba, failing to pick out his teammate with a ball around the back. The Billy Goats hit their opponents on the counter and made good ground down the right, but the Colombian striker could not keep the momentum going.
19 minSHOT! Francis Coquelin afforded plenty of room to shoot from the edge of the box, sending the ball narrowly wide from 20 yards out. The defensive midfielder has not scored since his time with Freiburg some four years ago.
21 minCHANCE! Pretty much the best chance either side has created so far; Ainsley Maitland-Niles crossing the ball towards the penalty spot where Jack Wilshere was waiting to meet it with his head. Right at Horn in the end.
23 minArsenal starting to assert themselves on the game a little more now, creating that chance for Wilshere and also coming close through Coquelin's long-range drive. As things stand, this point will be enough for the Gunners to make certain of top spot.
25 minThe onus is on Koln to create chances and find a breakthrough goal, which so far has eluded them. Just the one win in the Bundesliga and Europa League for them all campaign, remember, with that solitary victory coming against BATE three weeks ago.
27 minSmart play from the hosts, with a ball from deep very nearly being latch on to by Klunter through the middle. Ospina was well positioned to collect in the end, however, and it is now Arsenal's turn to throw some bodies forward.
29 minThe Billy Goats failing to make the most of their opportunities at the moment, as Osako opts for goal rather than sliding in one of his teammates. The poor decision looked even worse after slipping as he pulled the trigger.
31 minArsenal, held to a goalless draw by Red Star Belgrade in their last European outing, unable to find a way through the Koln defence in the opening third of this match. No pressure on them to do so, though - a point is all they require tonight.
33 minOFF THE POST! Coquelin is played in behind down the left and strikes the post with his attempt. The angle was against him, but he so nearly picked out the small gap at the near-post, which Horn may or may not have had covered.
35 minStill no breakthrough in the other Group H game, either, so that table remains as it was. Arsenal will be able to put their feet up for the visit of BATE in two weeks' time at this rate; a point all they need from this game to claim top spot.
37 minSHOT! Welbeck had a couple of players to pick out in the box, but he had the confidence to cut inside and bend the shot wide of the target. Not seen a great deal of the Englishman in the opening 37 minutes of this Group H tie.
39 minFC KOLN SUB! Good play from Arsenal, with the ball being played through for Welbeck, who in turn sends the ball into a central position. Skipper Maroh got a toe to it, pulling his hamstring in the process - Konstantin Rausch is on in his place.
41 minFour minutes to go until half time and Arsenal looking very comfortable. Not too dissimilar to Man United last night, in fact, although the Red Devils would go on to collapse in the second half and miss out on the point they were holding out for.
43 minMaitland-Niles puts his boot through the ball 18 yards from goal, with the shot being well blocked. Koln then counter but, not for the first time today, Osako lets his side down somewhat by overhitting the left-sided cross.
45 minElneny lofts the ball into the box from a deep free kick, which Horn was able to punch clear. Giroud then unable to return to the ball to Wilshere as Arsenal attempted to keep the attacking move alive, likely ending their hopes of a first-half goal.
45+2 minHALF TIME: FC KOLN 0-0 ARSENAL
6.51pmThe referee brings the first half to a close, with neither side able to find a way through in a goalless opening 45 minutes. Not a great deal between the two sides so far, but it is Arsenal who have had the better of the chances and they will argue that they should be in front.
6.54pmIt took Arsenal just a couple of minutes to register their first meaningful shot of the first half, with Ainsley Maitland-Niles - an ever-present in the Europa League this term - testing Timo Horn. A Jhon Cordoba effort aside, which David Ospina easily managed to keep out, Koln barely troubled their opponents in the opening 45 minutes despite needing all three points.
6.57pmArsenal were the side looking more likely to open the scoring as the half-time whistle approached, as Francis Coquelin sent one shot wide from 20 yards and another against the outside of the post from a slight angle. Arguably the best chance of the lot fell Jack Wilshere's way, however, heading the ball into the hands of Horn after being picked out by a Maitland-Niles cross.
7.00pmBENCH WATCH!
The home side have already been forced into making one change, bringing on Rausch for Maroah. Arsenal have a full selection of back-ups to choose from, meanwhile, with talented youngsters Nketiah, Nelson and Willock among them.
FC KOLN SUBS: Kessler, Olkowski, Risa, Lehmann, Nartey, Bisseck
ARSENAL SUBS: Macey, Sheaf, Willock, Iwobi, Nelson, Akpom, Nketiah
46 minRESTART! We are back under way at the RheinEnergieStadion, where Arsenal manager Wenger has made a change at the break by bringing on Iwobi for Welbeck in attack. Not sure if that is tactical or injury related.
48 minWenger may not have wanted to risk Welbeck for any longer than 45 minutes, as he eases the England international back to full fitness. Welbeck looked fairly bright in the first half, maybe doing enough to warrant a place in the side to face Burnley.
50 minYELLOW CARD! Wilshere is unlucky at one end, failing to find his feet to get a shot away, and then Debuchy lunged in on his opponent to earn the game's first yellow card. An open feel to the early stages of the second period.
52 minArsenal still look very comfortable at the back, but they have been unable to show that extra bit of quality needed at the other end of the field to find a way through. A reminder that a second-successive Group H draw will send the visitors through.
54 minWenger's men probing away in search of that first goal of the night in Group H, with BATE Borisov and Red Star Belgrade also locked at 0-0 in Belarus. The Frenchman may well be thinking of making a second change in the next five minutes or so.
56 minFC KOLN SUB! Arsenal could do with stepping up the pace a little more, which is not easy with 11 different players starting the match compared to last weekend's win over Spurs. Koln have made a second change - Cordoba replaced by Olkowski.
58 minYELLOW CARD! Billy Goats winger-back Klunter is the second player to receive a caution for his challenge. The second half following a similar them to the first - Arsenal well on top, without really troubling Timo Horn.
60 minCHANCE! The home side's best chance of the evening so far, with the ball bouncing nicely for Sehrou Guirassy - in far too much space inside the box - to hit. Poor connection in the end, though, and Ospina comfortably collected.
62 minGOAL! FC KOLN 1-0 ARSENAL (SEHROU GUIRASSY, PEN)
63 minSehrou Guirassy and Debuchy tangle legs inside the box, leading to the referee pointing to the spot. The young French striker converts from the spot, smashing the ball right down the middle to give Koln a 1-0 lead against the run of play.
65 minAgainst the run of play, the Bundesliga basement boys have taken the lead here. Certainly makes things a little more interesting, as Arsenal are now under pressure to step things up in an attacking sense - all a bit stale so far.
67 minSAVE! Home keeper Timo Horn with another fairly routine stop, this time to keep out a Per Mertesacker header. Red Star still unable to find a way through against BATE, so Arsenal remain four points clear at the Group H summit.
69 minSAVE! Arsenal have certainly stepped things up since going behind, with Wilshere now trying his luck with a well-hit shot. A little more difficult for Horn, but he again managed to punch the ball well clear, and the same player then glanced a cross over the bar.
71 minARSENAL SUB! Chambers's comeback has lasted a good 70 minutes; Reiss Nelson taking over from him down the flank to provide some extra attacking support. Arsenal, in control for large parts, have 20 minutes to find a goal.
73 minFC KOLN SUB! Stoger has made his third and final change, introducing Lehmann for Osako as we enter the final 17 minutes of the match. Arsenal well and truly dominating things now, but Giroud is currently the only player in the opposition box.
75 minCHANCE! It is still goalless in the match between BATE Borisov and Red Star, so Arsenal are still on course to finish top regardless of this result. Giroud is played in over the top and took the ball down brilliantly, but he was unable to get it out of his feet and the shot never arrived.
77 minFollowing a two-minute stoppage for Jannes-Kilian Horn - the brave defender who got back to thwart Giroud - the Arsenal corner finally arrives. Easily dealt with, once again, as the Gunners continue to struggle for ideas in the final third.
79 minAs far as Koln are concerned, they are now up to third in Group H and just one point adrift of Red Star Belgrade, who they face in Serbia in a fortnight. Wenger still has a change available to make, which he will no doubt use shortly.
81 minThe German side, without a win in Bundesliga all season, standing firm at the back. No way through for the Gunners, who are close to being shut out by the opposition for the second European match in succession. Nketiah being readied to come on...
83 minARSENAL SUB! Jack Wilshere attempts to loft the ball into the box for Olivier Giroud to meet, but it was a tad weak and cleared away. Nketiah is now on for Debuchy, as Wenger changes things around in search of a late leveller
85 minArsenal not quite throwing the kitchen sink at Koln just yet. Been a very flat second-half showing from the visitors, who are heading for a third defeat in their last 16 matches - two in the Premier League and now one in Europe.
87 minYELLOW CARD! Sehrou Guirassy, who is looking increasingly like being the matchwinner, is cautioned for catching Mertesacker. Not the most damaging of defeats for Arsenal, but disappointing nonetheless as things stand.
89 minSAVE! Really good play from Nelson, who has come closer than any of his teammates to finding a way through. The youngster wriggled through and got a shot away, which Horn did well to keep out. Time fast ticking down now!
90+1 minThe full-time whistle has blown in Belarus, where Red Star Belgrade have been held to a goalless draw by BATE Borisov. That is a big result, as it means that Arsenal have topped Group H with one game to spare, regardless of this likely loss.
90+3 minFULL TIME: FC KOLN 1-0 ARSENAL
8.02pmThe referee blows for full time, meaning that FC Koln - winless in the Bundesliga after 12 matches - are in with a real shout of qualifying for the last 32. The German side, who earned the win through a second half Sehrou Guirassy penalty, now require victory away at Red Star Belgrade in two weeks' time. Arsenal, regardless of this surprise defeat, will go through as Group H winners.
8.04pmThat concludes Sports Mole's live text coverage of events at the RheinEnergieStadion. An on-the-whistle report can be found by clicking here, while updates from Everton's meeting with Atalanta BC can be followed here. Thanks for joining!