"At PSV they were strong at the time he was manager," he told the club's official website.
"They were champions for three years, which shows how strong they were. They were very difficult to play against.
"He knows a lot about me because I scored goals in Holland but that is different and we are now in England, a new challenge for me.
"Because he knows me it doesn't mean that I don't have to show a lot, I have to show him and work hard and impress him again.
"Everyone is excited and wants to impress the new manager, so there is a challenge for everybody.
"Those players that weren't playing have a new chance to impress, and those that were now need to show more to keep their position."