He told manutd.com: "He's been outstanding. He is up there as one of the five best players in the world. He's learnt that the game is not all about doing fancy tricks, you need to do them at the right time. He's found the perfect balance now of proving hugely effective by scoring and making goals, whilst still being able to throw in the odd trick and entertain the crowd.
"I believe Sir Alex is probably one of the few managers in the world who could manage a player like Ronaldo. Had Ronaldo been anywhere else I think he would be a different player – I've no doubt about that. Sir Alex is hard enough to put him in his place, but he's also soft enough to encourage him as well."