Arsenal manager Arsene Wenger lamented a knee injury to Theo Walcott which overshadowed the 3-1 win against Birmingham.
The England forward was making his first start of the season for the Gunners, having been sidelined since August because of a back problem.
However, following a strong, sliding challenge by Blues defender Liam Ridgewell, Walcott eventually hobbled out of the action just after the half-hour.
Walcott will undergo a scan to assess the damage, which could now signal another spell on the sidelines for the World Cup hopeful.
"It is difficult to assess at the moment, whether it is a ligament which is twisted or just a kick," said Wenger. "The fact he says he felt a little unstable when he was running is not good.
"We will scan him. If he has just a kick, then he has a chance to play on Tuesday (away to AZ Alkmaar). But I believe he will not be available. It is not a cruciate problem, but it could be more than a week."
Source: Eurosport