Arsenal defender Per Mertesacker will be out for months after manager Arsene Wenger confirmed that the German is suffering from a knee problem that he picked up in their pre-season game against Lens. The defender did not travel with the Arsenal squad for the US tour and is likely to miss a major part of the campaign, putting the manager in a dilemma in terms of options at the back.

Gabriel is suffering from tonsillitis and is another player who has dropped out of the tour along with Laurent Koscielny, who is on an extended holiday following his participation in the Euros. Calum Chambers and Rob Holding are expected to marshal the defence at the back in the absence of the experienced trio when the Gunners take on the MLS All Stars at San Jose on Thursday, 28 July.

Wenger revealed that Mertesacker has had surgery on his knee in Germany but there is no clear timeline on his return, which is expected to spill over to a few months given the extent of the setback. The manager reiterated that they are short on the experience front in defence and will look to bring someone in at the earliest before their season opener against Liverpool on Sunday, 14 August.

"We have bad news on Per Mertesacker. He played in Lens on Friday night, he finished the game and had a little pain on his knee. We found out the next day that it was much more serious than expected. He had surgery yesterday in Germany. It all went well. I know you will ask me for how long he will be out. I don't know that, it's [some] months, but I don't know [exactly] how long he will be out for," Wenger told Arsenal's official website.

Per Mertesacker
Per Mertesacker picked up a knee injury against LensGetty

"We have to look for an option to get a bit more experience. We will see some of our young centre backs on Thursday as well. With Per being out, we are a bit short on the experience front and we are looking to bring somebody in," he added.