Ozil has been repeatedly criticised for his form since becoming Arsenal's record signing, and Ballack admits that the way the World Cup winner has responded to his troubles is a concern.
"A player like him with his ability should have tried to stay longer at Real Madrid," the former Chelsea midfielder told Sky Sports News. "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.
"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."
Ozil was one of the Arsenal players singled out for criticism following the 2-0 loss to Borussia Dortmund in the Champions League on Tuesday night.