Arsene Wenger has expressed concern over a knock picked up by Abou Diaby in Arsenal's victory over Bolton at the weekend.
The French midfielder was replaced in the 72nd minute of the 4-1 success, having only come on as a substitute a few minutes earlier.
He suffered an ankle injury following a challenge by Paul Robinson and Wenger is now waiting to discover the extent of the damage.
Diaby is set to undergo a scan which Wenger hopes will reveal no major problem, as the Gunners manager can ill-afford to lose another key player.
"It was a bad tackle. Diaby is not in a very good shape," Wenger said in The Sun.
"He cannot move his leg at the moment so we must wait to see if we have got away with it."
Robin van Persie, Nicklas Bendtner, Theo Walcott and Aaron Ramsey are all currently sidelined and the season is just a few weeks old.
Arsenal kick off their UEFA Champions League campaign with a home game against Braga on Wednesday.