He told the Daily Mail: "He learned a lot in Germany.
"He had to run and put energy into his game. When we had power training, he'd say, 'I don't like that coach, don't worry, I will play well when I have to' but I think he changed because I can see his body is strong.
"He came back really well and is playing at Manchester City with some of the biggest players in the world. He sees the solutions quicker than anyone else and they expect the ball and can control it even when he plays it so hard. It is unbelievable to see. He is a leader of the team. He has all the qualities you need."
Been played with Cruyff at Feyenoord and is aware of the comparison.
"You can say they both read the game," said the Dutchman. "Kevin still has to show it in the Belgium team. Mentally, they must still make a step. They have been missing a leader and hopefully Kevin, with his confidence, can lead them to something. I'm curious to find out."