Henrikh Mkhitaryan has been ruled out for up to six weeks with a fractured metatarsal.
Mkhitaryan, 29, was substituted at half-time during the 2-0 home defeat to Tottenham Hotspur in Wednesday’s Carabao Cup quarterfinal.
That match came just three days after he had scored two goals in the 3-2 loss at Southampton.
The Armenian playmaker is expected to miss the Gunners’ next eight matches, including the Premier League visits to Liverpool on Dec. 29 and Manchester City on Feb. 3.
Arsenal said in a statement that full-back Nacho Monreal would have his fitness assessed ahead of the Boxing Day match at Brighton & Hove Albion, while centre-back Shkodran Mustafi is also expected to return to training this week.
Hector Bellerin, however, is not expected back for another two weeks as he recovers from a calf injury.