Arsenal could be without key defender Per Mertesacker for the rest of 2016.

According to El Confidencial journalist Kike Martin, the German centre-half could miss as many as five months with a knee problem.

Mertesacker did not travel with the Gunners squad for their pre-season tour of the USA despite playing in last week's friendly with French club Lens.

It is understood that the 2014 World Cup winner has sustained a knee injury which according to Martin will keep him out for the remainder of the year.

Responding to a post on Arsenal's Twitter account, Martin wrote: “@arsenal Mertesacker has a knee injury. He COULD BE 5 months out. Bad luck! #afc."

This news comes from the man who was first to report that Alexis Sanchez was set to join the Gunners from Barcelona in 2014.

Hopefully for the North Londoners, his information is wrong…

Arsenal did confirm that Mertesacker's knee was the reason for him missing the trip Stateside.

The Gunners Tweeted: "You may have spotted one notable absentee. @mertesackerhas a knee problem and won't be part of #ArsenalUSA."