Danny Welbeck has had surgery on a broken ankle but Arsenal manager Unai Emery does not know if the England striker will return this season.
The 27-year-old suffered the injury during Thursday's Europa League draw with Sporting Lisbon and had to be carried off on a stretcher.
"It's a big injury. He had an operation on Friday," said Emery.
When asked if Welbeck would play again this season, Emery replied: "The doctor can answer that better than me."
Welbeck, who has scored five goals in 14 matches for Arsenal this season, had been included in the latest England squad for games against the United States and Croatia next week.