Mesut Özil has struggled to maximize his potential during his first year in the Premier League with Arsenal.

Michael Ballack believes Özil should have fought to remain at Real Madrid.

"What's happened with him? I don't know," said Ballack. "There must be something behind [the scenes] because his head is mostly down, the body language is not improving even with the world champion [medal] in the pocket.

"I don't really know what's happened over the last year since he moved from Madrid to Arsenal.

"A player like him with his ability should have tried to stay longer at Real Madrid. That is my opinion. You could see there was a little bit trouble, a little bit moaning. I think he played well but you need time to adapt at a club.

"If there is some ups and downs [at a club] you need to fight these things and now it's a little bit the same situation. He got criticized here [at Arsenal], he's not at his best but I don't see a reaction.

"A player like him with his ability should show a reaction but he never was the strongest player in terms of fighting, body language. That's his weakness - especially in these situations now when he can't use his technique and his vision."