"I think Fernando already knows how difficult the Premier League can be, but he did really well last year. He is only 23 and can only get better and better," said the Dutch international.
"The only thing he has to be careful about is that people are starting to know him now. But for a player like him, with his qualities, it is always going to be difficult to play against them.
"He showed that last season and can only improve. He knows that and the defenders know that as well. They will be afraid of him. If he stays fit he can do even better than last season."