Arsenal manager Mikel Arteta has revealed that the luckless Takehiro Tomiyasu faces "a while" on the sidelines with a calf injury.
Since departing Bologna for North London in the summer of 2021, Tomiyasu has struggled to string together a consistent run of performances owing to a plethora of fitness problems.
The Japan international played second fiddle to Ben White for most of the 2022-23 campaign, which was cut short for the right-back when he underwent a knee operation in March.
Nevertheless, Tomiyasu remains a fan favourite at the Emirates and played his way back into Arteta's starting lineup this season courtesy of several strong defensive performances, as well as improving his attacking output.
Tomiyasu scored his first goal for the club in October's 5-0 thrashing of Sheffield United, and the 25-year-old - who is expected to sign a new-and-improved contract in the coming months - featured from the first whistle against Wolverhampton Wanderers at the weekend.
However, the defender was forced off in the second half of that 2-1 win, although Arteta described his substitution as precautionary and expressed hope that he would be fit to face Luton Town on Tuesday night.
Tomiyasu was nowhere to be seen at Kenilworth Road, though, and speaking to the media after the Gunners' enthralling 4-3 triumph, Arteta delivered the crushing blow that the Japan international would not be making his comeback anytime soon.
"We had a scan and it's not good news. He's got an injury in his calf and he's going to be out for a while I think," football.london quotes the Spaniard as saying in a press conference.
While Arsenal have not pencilled in a return date for Tomiyasu, he is expected to be missing for at least four and potentially up to six weeks, ruling him out of meetings with Aston Villa, Brighton & Hove Albion and a double-header with Liverpool.
The Gunners were highly vulnerable from set-pieces without Tomiyasu in the side against Luton, conceding headers to Gabriel Osho and Elijah Adebayo in such circumstances after Gabriel Martinelli and Gabriel Jesus had netted themselves.
David Raya did not cover himself in glory for Adebayo's goal, and the Brentford loanee was also at fault for Luton's third, allowing a Ross Barkley shot to fly into the back of the net under his body.
However, Raya's blushes were spared thanks to a Kai Havertz equaliser and dramatic Declan Rice winner, as the £105m midfielder headed home into the bottom corner with the last chance of the game to send the away end into pandemonium.
"This is the incredible thing about football, emotions and what you live together with a lot of people. It was a special night. Credit to Luton, the atmosphere they created, how they were coached, how they made it difficult for us, but we found a way to win," Arteta added. "The resilience, and the character, and the quality and desire to win that the team showed was great."
Raya's blunders naturally reignited the discussion surrounding Arsenal's goalkeeping situation as Aaron Ramsdale remains out in the cold, but similar to when the latter made a pair of mistakes versus Brentford, Arteta did not directly address Raya's display.
"We have to defend better the situations as a team. There are certain things leading to the goals. It's not about blaming. We have never done it and we won't do it now," Arteta said when asked specifically about Raya.
"It's about how the team reacts because it's going to happen. I love that response. I think we can defend the goals much better for sure."
Arsenal's fourth top-flight win on the bounce has seen them temporarily open up a five-point lead at the top of the Premier League table, and a trip to Aston Villa is next up for the Gunners on Saturday evening.
