Cristiano Ronaldo believes "everything is possible" after firing Manchester United to an important Champions League win at the end of a tough night against Villarreal on an individual and collective level.

Having kicked off Group F with a shock loss at Young Boys, the Red Devils were under no illusion about the need to kickstart their continental campaign against Unai Emery's visitors.

Villarreal broke United hearts in the Europa League final four months ago and were on course to inflict another chastening loss after Paco Alcacer finally beat impressive David De Gea early in the second half.

But Alex Telles scored a stunning equaliser and Ronaldo produced a box-office finale, smashing home in the fifth and final minute of stoppage time to secure a 2-1 win at rocking Old Trafford.

"I'm so happy," the match-winning Portuguese said. "The game tonight was not my best. I didn't play so good.

"But sometimes I play good I don't score. Today I don't play good and I score.

"Very important. We knew if we didn't get points today it would be tough to go through to the next stage but now everything is possible, everything is open and we believe we go through."

Ronaldo scored with his only shot on target against a Villarreal side that made life difficult for the hosts from the outset.

The Carabao Cup exit to West Ham and Premier League loss to Aston Villa appeared to have knocked United's confidence, but the remarkable conclusion to Wednesday's game might provide a timely shot in the arm.

"It was a very, very difficult game," Ronaldo said. "Villarreal played so good, create many chances.

"We struggled a little bit because we knew before the game that we must win the game.

"It was tough, the team was a little bit nervous especially.... well, first half and second half, to be honest.

"But we had a little bit of luck that we didn't have in the last game (against Villa on Saturday).

"It was good, great attitude from our players. The fans pushed us a lot, which I have to say thank you to all of them.

"This is what we need sometimes when we're a little bit down, when the team is not playing well, but an important win."

Ronaldo broke the all-time Champions League appearance record on Wednesday, moving onto 178 appearances and clear of former Real Madrid team-mate Iker Casillas.

The 36-year-old has won the competition five times during that record-breaking stretch, including the 2008 edition with United, and is looking forward to making more history back at Old Trafford.

"This is why I come back because I miss this club a lot," he told BT Sport.

"I made history in this club and I want to do it again.

"I have to say thank you to all of them – not only from me but to push the team which will be very important, especially this season. Another chapter, yes."

United welcome Atalanta to Old Trafford in their next Group F match, before heading to Bergamo for the reverse fixture in early November.

Villarreal have back-to-back matches with Young Boys buoyed by an impressive performance in defeat to United.

"It's a short competition, and we only have a point," manager Emery said. "Now we are in need.

"The other teams have an advantage over us. But if we carry on like this, we'll pick up some wins.

"In football, you don't always win because of the chances you created. Errors can also penalise you.

"You need to analyse why we lost, but we are trying to look positively. We think this is the path to follow."