Rijkaard knows the former Ajax midfielder well and said: "He's a creative player, potentially a great one and someone who can create and score goals.
"He's strong on both sides of his body. He can play in midfield, attack and out wide. He has a good mentality and a winning character."
On Real Madrid, Rijkaard added: "They've made a lot of new signings, all of which will have a great desire to do well. So, it's logical that they have started the season the way they have."