"Last week he was not scoring goals and people were asking whether he was fit. Tonight he has scored two important goals and I am really pleased with him," said the boss.
"I was also pleased with his contribution against Debrecen because he was working very hard - not scoring - but creating chances and space for his teammates.
"Today you could see he was a constant threat.
"He is a very good player, but the main thing for us, is that he keeps his mentality.
"He is keen to learn and can improve. You saw his quality today. We have a very good player and hopefully he will get better in the future.
"He's now fit and we are working hard with him. If he cannot play one or two games, we have Kuyt who can score goals or maybe Ryan [Babel] who did well when he came on today.
"Hopefully he will stay fit and score a lot of goals for us, but we have different options and I think we can manage."