Arsenal defender Per Mertesacker could be out for as long as five months due to a knee injury.

Mertesacker made 24 appearances for the Gunners last season, before missing the end of the campaign.

Arsenal is yet to put a timeframe on a possible return, however, El Confidential journalist Kike Marin has reported that the 31-year-old is set for an extended period on the sidelines.

“Mertesacker has a knee injury. He could be 5 months out. Bad luck!” Marin tweeted.

If Metersacker is ruled out for five months, it means Arsene Wegner will likely seek to sign a new defender, with the Gunners only fit central defender being 21-year-old Calum Chambers.

Mertesacker did not travel with the rest of the team for the pre-season tour to America.