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."
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."
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