"He is unbelievable, a really good player," said the Dutch international.
"I have never seen someone who is that quick with the ball. I don't think anyone is as quick as Fernando is with the ball at his feet.
"He showed it again against Middlesbrough and if you have a player like that in your team you have to be really happy.
"He is definitely going to get better as well because he is still very young and he has only been playing football in this country for just over six months.
"No disrespect to Atletico Madrid but I think Liverpool is the real thing, a really big club, one of the biggest in Europe and with the kind of players he has behind him here - the likes of Steven Gerrard, Javier Mascherano, Xabi Alonso - he is only going to improve.
"It is great for everyone in the team to have a player like Fernando up front because he is unbelievable.
"I think he played really well against Inter in the week but he was even better against 'Boro.
"The hat-trick he scored against them was his second of the season already so that is really good for him and for us."