"People are saying stuff about me looking slower or heavier or whatever but to be honest that's rubbish," he told the club's official magazine.
"If anything I have lost weight and have less body fat than I did last year. We are constantly monitored in both those areas.
"I am working as hard as ever and I don't feel as if I have done anything drastically wrong this season for people to comment on.
"What I don't do is let anything that is thrown at me get in the way of training or learning.
"I take criticism in my stride. All the players have dips and I am staying positive. I know I give 100 per cent in every match.
"Of course I am not the finished article. I have lots to learn and would be a fool to think anything else.
"I believe in my ability and I think City fans know what I am capable of. It is just a matter of finding the form I was in last season."