Arsenal midfielder Tomas Rosicky has been ruled out for up to three months because of a thigh problem.
The 35-year-old, whose contract expires in the summer, suffered the injury in his first appearance for seven months against Burnley on Saturday.
Czech Republic international Rosicky joined Arsenal in May 2006.
Asked if Rosicky had played his last game for the Gunners, boss Arsene Wenger said: "I hope not but the injury is quite a serious one."
Rosicky, who has made 246 appearances for Arsenal, signed a one-year contract extension last summer.
Welbeck back in action
Meanwhile, striker Danny Welbeck made his return to action for the under-21s on Friday.
The England international, 25, has been sidelined since April 2015 after injuring himself in a 0-0 draw with Chelsea, but played one hour in the game against Brighton.