Arsenal will be without defender Takehiro Tomiyasu (25) for the start of their Premier League campaign as the Japan international will be out for weeks with a knee injury, manager Mikel Arteta said on Sunday.
Tomiyasu was left out of Arsenal's pre-season tour in the US due to the injury, and was also absent from Sunday's 2-0 win over Lyon in London.
"I think it will take weeks on that one, unfortunately," Arteta told reporters of Tomiyasu's injury.
"He's going to have to be patient and work through it because I think it's going to take a few weeks."
Dutch defender Jurrien Timber, who missed most of last season due to an anterior cruciate ligament tear that required surgery, also missed Sunday's game with a knee injury but is expected to rejoin the first team in the next week, Arteta added.
Arsenal, last season's runners-up, begin their Premier League campaign on Saturday at home against Wolverhampton Wanderers.