Arsenal defender Johan Djourou is to miss the rest of the season after dislocating his shoulder against Manchester United.
Djourou sustained the injury during the latter stages of Arsenal's 2-0 FA Cup defeat at Old Trafford on Saturday.
Racing back to try and deny Javier Hernandez a goalscoring chance, the Swiss centre-back collided with team-mate Bacary Sagna.
He stayed down in agony and there was a lengthy stoppage as medics administered treatment before carefully placing him on a stretcher.
Arsenal had to see out the remaining minutes with just ten men, having already used all three of their allotted substitutions.
The extent of the damage has now been confirmed and Djourou will play no further part in the Premier League this term.
"Unfortunately we lost Johan Djourou for the rest of the season," said Arsene Wenger. "Dislocated shoulder. Season over."
The league is Arsenal's last remaining opportunity to claim silverware following a disastrous couple of weeks that has seen them lose the Carling Cup final and bow out of the UEFA Champions League.
News of Djourou's injury will compound Wenger's misery as he has been a key performer in the heart of Arsenal's defence.
The 24-year-old missed virtually the entire 2009/10 campaign following knee surgery but has earned rave reviews for his performances this term.
With Thomas Vermaelen a long-term absentee due to an Achilles problem, Wenger will be relying on Frenchmen Laurent Koscielny and Sebastien Squillaci for the next couple of months.