Mertesacker wins Arsenal praise for Dortmund performance
Gunners No2 Pat Rice told arsenal.com: "Per, from my point of view, is a terrific player. The amount of games he has played for the German national side means he cannot be a bad player.
"It is impossible. He is showing that gradually with us. I thought he was terrific tonight alongside Laurent Koscielny and I can only see him getting better and better when he gets used to the Premier League."