"He can do even better. In the last three games he's been really good. He's improving and his mentality, workrate and movements show his ability," said the boss.
"Still I think he can do better. The main thing is the mentality of the player. I always say the same: he's keen to learn and that's the main thing. That means he will improve. How much depends on him.
"£20 million is a massive figure for us, so we knew he was good. But the main thing when we decided to bring him here apart from his quality was the potential, his age and the future he had. So, we are very pleased now but he can still improve."