Arsenal have received a massive blow in the form of Per Mertesacker, who is out of their tour of USA with a knee injury. The German was the most experienced defender on the tour and would now be on the sidelines along with Gabriel, who is out with tonsillitis.

The Arsenal official website tweeted that Mertesacker was not part of the travelling party while Granit Xhaka will make the group and is likely to make his first appearance for the Gunners against the MLS All-Stars. The recent news is a major problem for the north London club, especially with Laurent Koscielny expected to miss the opening few games thanks to his extended holiday after his travails with France in the Euros.

Mathieu Debuchy, Nacho Monreal, Rob Holding, Hector Bellerin, Calum Chambers and Kieran Gibbs are the other defenders in the squad. Arsene Wenger, most likely, will have to manage with Chambers and Holding in the centre of defence for the time being in the absence of the experienced pair. Chambers was culpable for conceding the first goal against Lens in their first pre-season friendly where he misjudged a header and allowed the French club to go through on goal.

Wenger has previously stated that he was in the market for a defender and would make a move in the market depending on the period of Mertesacker's absence. The Gunners are also in the market for a striker and have been linked with a myriad of targets such as Gonzalo Higuain and Mauro Icardi. Danny Welbeck is currently out for the major part of next season with a knee injury while Olivier Giroud is likely to miss the opening few games following his participation in the Euros.

Per Mertesacker
Mertesacker will be unavailable for Arsenal in the US Tour.Getty

The north London club have four friendlies lined up before their Premier League opener against Liverpool at the Emirates stadium on 14 August. The Gunners will be hoping to get a few signings done before the contest, failing which they could be short for the fixture, given that Alexis Sanchez is still recovering from an ankle injury.