The 6ft 6in German defender has received stick from some quarters since his signing in the summer transfer window but Wenger is certain he can silence the critics.
In fact, Wenger was happy to compare his potential influence with an Arsenal legend in former captain and defensive stalwart Tony Adams.
Wenger said: "He is a little bit like that (Adams). Not the quickest but he uses his brain well. Mertesacker is getting stronger in every single game. He is getting more aggressive. I like him personally. He's a very intelligent player and will be a big asset for us.
"I think Mertesacker can be a talker. Trust the Germans, he is a fighter. I am happy with what I see from him. Many times people judge you quickly. I am happy with the buys we made. I am not happy with the results, that is completely different."