Arsene Wenger to step up search for a defender after Mertesacker injury as Arsenal train ahead of MLS All-Star clash

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Arsene Wenger has been forced to step up his search for a new central defender after Per Mertesacker was ruled out for five months.

The German centre-back finished Friday night’s 1-1 draw with Lens with a small pain in the back of his knee but when he had the injury re-examined on Saturday morning, damage to his ligament was detected and the only option to cure was surgery.

While Arsenal’s squad travelled to the United States for two friendlies against the MLS All-Stars and Chivas, Mertesacker returned to Germany to undergo an operation and Wenger is not putting a time on when he will be back.

Arsene Wenger took Arsenal's first training session in America after landing in San Jose on Monday

New signing Granit Xhaka was also present and Wenger confirmed he will play against the MLS All-Stars

Youngsters Krystian Bielik, Jeff Reine-Adelaide and Gedion Zelalem also trained with the first team squad

But now Arsenal’s manager has to find cover, as Laurent Koscielny is still on holiday after his exertions at Euro 2016, meaning Gabriel, who has also missed the US tour because of tonsillitis, and Calum Chambers are the only centre-backs available for the opening fixture against Liverpool.

Valencia’s Shokdhran Mustafi could be a target and while Wenger would not comment on the players with whom Arsenal have been linked, he admitted the need to make an addition has become pressing.

‘We have bad news about Per,’ said Wenger. ‘He played against Lens and had a little pain but then we found out it was worse and he had surgery. 

Egyptian midfielder Mohamed Elneny looked focused on his football in the 35 degree heat of California

Francis Coquelin (right) clearly doesn't change his style in training after flying into a challenge 

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'I do not know how long he will be out but it is definitely going to be for a few months.'

‘We need cover. We play some young players on Thursday (against the MLS All-Stars) but with Per being out, we are now a little short and I will have to bring somebody in.’

Wenger’s main search this summer has been for a top class striker. He failed in an attempt to land Leicester City’s Jamie Vardy and now he has been warned by Lyon they have no interest of entering into negotiations Alexandre Lacazette.

Jack Wilshere will hope to get a full pre-season under his belt as he aims to put injury issues behind him

Arsenal's latest signing Rob Holding worked in the gym alongside compatriot Alex Oxlade-Chamberlain

Highly rated winger Chris Willock also travelled with the squad and will hope to impress Wenger 

‘Arsenal made an offer of €35m which Lyon didn’t accept for one reason alone – we will keep Alexandre Lacazette,’ read a statement released by the French club.

Asked what made of Lyon’s claim, Wenger said: ‘Lyon are comfortable with their own statements. I think in situations like this it is always best to keep things as secret as possible. If we sign someone, we will announce it. Until then, I can’t say much more than that.’

Jack Wilshere sat by Wenger’s side for the press conference in San Jose and he spoke for the first time about England’s exit from Euro 2016, admitting: ‘We just were not good enough against Iceland. It was that simple. The feeling (of bitter disappointment) is always there.’