Goalkeeper Petr Cech could miss Arsenal's games against FK Qarabag and Fulham after injuring a leg during Saturday's 2-0 win over Watford.
The 36-year-old appeared to tweak a hamstring after taking a goal-kick just before half-time, and was replaced by Bernd Leno, who made his league debut for the Gunners.
"Maybe he'll be out for two or three weeks," said manager Unai Emery.
Arsenal play Qarabag and Fulham next week, before the international break.
The Gunners are then back in action against Leicester on 22 October.