Mesut Ozil should not have left Real Madrid for Arsenal, according to former Germany and Chelsea midfielder Michael Ballack.
The 25-year-old has become the scapegoat of the Gunners' uncertain start to the season, which continued with a 2-0 defeat to Borussia Dortmund in the Champions League on 16 September.
Ozil's performances since his £42.5m move to Arsenal have failed to justify his inflated valuation and Ballack believes the playmaker should have remained in Spain.
"What's happened with him? I don't know," Ballack told Sky Sports. "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 [of] moaning. He played well but you need time to adapt at a club.
"If there are some ups and downs [at a club], you need to fight these things. And now it's a little bit [of] the same situation. He got criticised 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."
With Arsenal overstocked with creative midfielders, manager Arsene Wenger has been forced to move Ozil from his favoured central role and into a wide-left position, with the French boss attempting to accommodate the likes of Aaron Ramsey and Alexis Sanchez in his first team.
But Ballack has joined the calls demanding Wenger reinstate Ozil in his preferred position behind the striker in order to see him return to his best form for Arsenal.
"When you a buy a player like Ozil you know his strengths and Arsene Wenger knows, I think, where he is at his best," Ballack said.
"If he [Wenger] thinks he can help the team more as a No.10, I think he would put him at No.10.
"In his [youth] when he grew up from Schalke and Werder Bremen, he was mostly in the [centre of] midfield so he felt very comfortable there but in terms of pace, he's good on the side as well.
"But he needs to learn how to defend as well because on these winger positions, you need to defend. At this level, if one player's out, you have no chance."