"I'm going to reserve judgement on a few things for a bit longer. There's no doubt if he can get back to his best he should be an asset, but he has to perform on the pitch," the Villa boss told the Birmingham Post
"He's obviously cost the club a sizeable amount of money, come with a biggish reputation and has scored goals in international football.
"Maybe he thought it would be easier for him to adapt but football is not like that.
"It's not as difficult if you've got loads of ability, you're fit and fresh and raring to go and have confidence, but confidence isn't as great as he'd want at the moment.
"We have a new fitness scheme but no matter what you do, and you can encourage and cajole, but eventually it is down to the player.
"Once I make my mind up I may stick with it, but at the moment I'm deliberating."