Arsenal boss Wenger: I signed Mertesacker for Stoke games
Stoke have become notoriously tough customers from set-pieces under Tony Pulis - but Wenger says Mertesacker could be key at both ends for his team.
"I expect some goals on set-pieces from Per because even in Marseille we had nine corners and they had one," he told arsenal.com. "Out of nine corners away from home you expect to be a bit more dangerous.
"I brought him here for more than this type of game [Stoke] because I feel he is a good player. He is a good organiser, he understands the game, he is an intelligent player and physically he is getting sharper and sharper in every game.
"He had no real preparation for the season and now you can see that we look less nervous at the back and he contributes to that."