Arsenal defender Laurent Kosciely has suffered an Achilles injury during Europa League semi-final second leg at Atletico Madrid.
The 32-year-old lost his footing off the ball and was in obvious distress as he clutched his lower leg. Laurent Koscielny was substituted just after 12 minutes with Calum Chambers coming on.
The injury could force him even to miss the World Cup 2018 in Russia.
"It doesn't look very good," said Wenger. "You can always hope that the scan will say something different but the first signs aren't very good.
"It looks like it could be ruptured although I'm a bit cautious - no-one can say that clinically at the moment.
"That depends on the scan. If he has ruptured it the chances are non-existent," Wenger added.
Achilles injuries usually mean at least six months out.