"He's getting his goals and he's doing it when he's still not 100% fit. He's carrying little knocks and niggles but he is going out and doing a job for us.
"I have to say, I've been surprised with how he has coped with the demands that have been placed on him.
"He wasn't playing regular football in Germany. He was in and out of the Bayern Munich team and had injuries as well.
"But he has come here and made a huge impact, not only on us but on the Premier League as a whole. I think everybody likes watching him play and we're benefiting from it."