holding ronaldo good

Well, there's food for thought in your discussion but I don't think he'll play under par because he wasn't allowed to go. Infact I still believe he didn't want to leave old trafford, all he wanted was a pay hike. Neither did he give a transfer request to the chairman nor did real madrid officially bid for ronalso. Both parties were only throwing arrows in the air.
Ronaldo also knows that he's still got four years left on his contract and if he does not play to his potential, United can virtually ruin his career by not letting him play in any proffesional match like what SAF had said. SAF has clearly mentioned that he rather keep ronaldo in the stands than sell him to madrid.
He may not be able to score as many goals as last season due to the arrival of berbatov but he will still be the same ronnie we saw last year and maybe even better.

No, I don't think he will play below par. If he were to do that, he would only be harming himself and denting his career. Remember, these lads are professionals employed to do stuff they are paid for. Besides, he might have wanted to go to Real Madrid, but he still was committed by his contract with MUFC. And this is where I agree with the UEFA president about respect for contracts. Players should not be allowed to forego their own signed contracts. If mutual departure can't work, well, they are bound by the contract and would have to respect it by abiding to it.