"Ronny is in a good spell. He has been scoring goals and playing well for a couple of months," said the Dutchman.
"The manager has made a target of 15 goals for him this season, but I think we should maybe lift that a little bit now.
"If he gets to 20 then, for sure, we will have a good chance this season.
"He scored two nice goals at Villa and the crowd reacted to him when he came on as a sub against Wigan.
"He enjoys working and training. He does everything well. He is a young guy who is still improving. He is living his life on the pitch and working hard.
"Cristiano is getting better and better. He is still only young, but he is more mature now as a footballer.
"He has loads of qualities with the ball, but is more aware now in terms of his positional play, the runs he can make, the other players who make runs for him, and of creating space for other players.
"I think it is his most productive season so far. He is scoring more goals and delivering more crosses. He has been excellent for us.
"I wasn't in England after what happened with Cristiano at the World Cup, but I can imagine what the papers and TV were saying.
"It was a country-versus-country situation and you do the best for your own country.
"The United fans have stuck with Cristiano and I think the opposing fans see the quality he has and the joy with which he plays the game.
"He will get occasional booing but that's all right. I thank that only serves to drive Cristiano on to even higher ground, to greater heights.
"Cristiano hasn't let what happened, and the reaction, affect him at all. He is a very strong guy and has shown that this season."