Jol said: "I can't predict the future. We want to keep him and hopefully he wants to stay. We have offered him a very good deal.
"He knows he is very appreciated at our club. If we want to be a top side we need players who can score more than 20 goals a season.
"He's not at that level yet but for a wide midfield player who can play up front and score that many goals, it is unbelievable."