Arsenal striker Alexis Sanchez will be assessed over the next two days to gauge the severity of the injury he suffered in Sunday's draw at Norwich.
The 26-year-old limped out of the 1-1 draw at Carrow Road at the weekend.
Boss Arsene Wenger defended Sanchez's selection, despite him suffering "a little hamstring alarm" in last week's Champions League over Dinamo Zagreb.
Arsenal also lost Laurent Koscielny and Santi Cazorla on Sunday, adding to a lengthy list of injured players.
|Arsenal injury list|
|Mikel Arteta||Midfielder||Calf strain|
|Francis Coquelin||Midfielder||Knee ligament|
|Theo Walcott||Forward||Calf strain|
The Gunners face Sunderland in the Premier League on Saturday, followed on Wednesday by a crunch last Champions League group game in Athens against Olympiakos, which they need to win by two goals, or a high-scoring one-goal margin, to reach the last 16.
Sunday's result meant Wenger's side missed out on the chance to draw level on points with Manchester City at the top of the Premier League.