Arsenal midfielder Lucas Torreira faces a spell on the sidelines after he suffered a fractured ankle in Monday's 2-0 FA Cup victory over third-tier Portsmouth, the Premier League side announced on Thursday.
The 24-year-old Uruguayan international was stretchered off early on in the fifth round clash but Arsenal have not indicated when he might return only saying he faces further specialist reviews.
"He (Torreira) was quite positive this morning. We don't know the extent of the injury," Arsenal manager Mikel Arteta said at his press conference ahead of this weekend's match with struggling West Ham.
"It's part of football, we have to adapt. It happens to other teams, we cannot cry about it."
Other players must also wait for their return with defender Sead Kolasinac predicted to be out until the end of March with a shoulder injury.
Portugal international Cedric Soares is nearing his debut for the club after signing on-loan from Southampton but the 28-year-old Euro 2016 winning full-back must wait another week before being available for full training.
There was more optimistic news regarding Scotland full-back Kieran Tierney whose first season with the Gunners has been ruined by injury.
The 22-year-old former Celtic defender has returned to full training after dislocating his shoulder in December.
"He's (Tierney) done two or three complete sessions. Hopefully he will join the squad soon," said Arteta.