Arsenal boss Mikel Arteta believes there is a chance David Luiz could play against Villarreal on Thursday.
The Gunners face the biggest game of their season as they are 2-1 down from the semi final first leg last Thursday.
They must win 1-0 or by two clear goals to progress to the final.
Brazilian defender Luiz recovered from a knee issue, played against Newcastle United on Sunday, but had to come off due to a hamstring issue.
"With David, it is always possible," Arteta told reporters.
"He was already saying before the game that he wanted to be available.
"He has made an incredible effort to be in the position that he is today. The fact that he played against Newcastle was already a big bonus, because he had surgery on his knee. With David you never know."