Arsenal boss Arsene Wenger says midfielder Francis Coquelin will be out injured until the end of the year.
The Frenchman had to abandon last Saturday's game against West Bromwich Albion after only 14 minutes and is not expected to be back before the start of the new year.
Welshman Aaron Ramsey is back in the squad and fit to face Dinamo Zagreb on Tuesday night.
"[Francis] Coquelin and [Mikel] Arteta are out," Wenger explained.
"Arteta is short-term and Coquelin is longer. How big the damage is we don't know but we will know for certain this [Monday] afternoon. Everyone from Saturday's game is available and [Aaron] Ramsey is available.
"It is at least a month [for Coquelin]. I'm a bit cautious as we have had so many bad surprises on the scans but the team for the next few months will be without Coquelin.
"It looks like that at the moment [we are getting more injuries than most clubs].
"I must say we have been hit very hard in November as until November and the Sheffield Wednesday game we had quite a good record and since then we lost a few players.
"But now we have Ramsey and for the weekend Oxlade-Chamberlain will be back as well. After that Walcott will be the next one. [As for] the players who have long-term injuries, basically some of them are from last season like Rosicky and Welbeck."