Arsenal centre-back Per Mertesacker will be sidelined for "a few months" with a knee injury, Arsene Wenger has confirmed, leaving the Gunners with a depleted defence for the start of the season.
Mertesacker injured his knee during Friday's preseason game at Lens and then needed surgery after discovering the full extent of the problem.
He stayed home as Arsenal traveled to the United States for a preseason tour, and Wenger confirmed Tuesday that the German suffered a long-term problem.
"We have bad news for Per Mertesacker," Wenger said at a news conference in San Jose, California, on Tuesday ahead of Thursday night's game against the MLS All-Stars.
"He finished the game [at Lens] and had a little pain in his knee. And he found out the next day that it was much more serious than expected. He had surgery yesterday in Germany and it all went well.
"I know you'll ask me for how long he'll be out, I don't know. A few months, but I don't know how many exactly."
- Arsenal FC (@Arsenal) July 26, 2016
The injury leaves Arsenal short of options for their opening Premier League game, when Laurent Koscielny will only recently have returned to training following France's Euro 2016 run to the final.
Gabriel Paulista also missed the U.S. trip with tonsillitis, but he should be back well in time for the Liverpool game on Aug. 14, with Calum Chambers the only other senior centre-back in the squad.
New signing Rob Holding, a 20-year-old who joined from Bolton, has yet to play a Premier League game but could be called upon quicker than expected if Wenger does not sign a more experienced defender in the transfer window.
"We have to look at all options to get a bit more experience," Wenger said. "We'll see some of our young centre-backs on [Thursday] as well. But with Per out, we are a bit short."
Arsenal face the MLS All-Stars in San Jose, California, on Thursday night before a game against Chivas de Guadalajara on Sunday.
Wenger also confirmed that Granit Xhaka will play against the All-Stars following his move from Borussia Monchengladbach this summer.