Rooney told the Daily Mail: "Ronaldo found ways he could improve until he was the best player in the world. He worked hard in the gym, he got tougher, he used to be smaller physically but he changed his shape. I would like to improve in other ways - I could get better at link-up play, I could score more goals, particularly with my head.
"At United everyone said Ronaldo didn't run back or defend, but when you see what he did, he was that good going forward, the rest of the team had to make up for him at the back. I've watched Ronaldo's first few games for Real Madrid and he seems to have improved again. He is even passing the ball a bit more now. He is definitely the best in the world.
"Some things inspire you. You look at a player like Fabio Cannavaro, who had a great tournament at the World Cup in 2006 and then won World Player of the Year. There were better players around but that tournament did it for him. It can make a difference."