"Per will have to get used to English football, particularly the speed of the game," he said.
"It is faster than the Bundesliga and will be a change for him, but he will cope. I am absolutely sure about that."
Lehmann and Mertesacker were in the German side that reached the semi-finals of the World Cup in 2006 and the goalkeeper has no hesitation in providing a glowing reference.
"The club will benefit from having him because he brings more quality to their defensive line-up. "