Ozil has faced criticism this season for some below-par performances since his move from Real Madrid last summer, but Mertesacker believes that his fellow German will be better for the Gunners next season.
"I think the second season will be much better for him because he's a fantastic player," the 29-year-old told Arsenal's official website.
"He has shown some great skills but he needs to be more consistent, which makes a difference at the end.
"Sometimes it's good to get criticism with the negative points - if you are intelligent enough, and he is an intelligent footballer. I think he will sort that problem out."
Ozil returned from a hamstring injury for Arsenal in the 3-0 victory over Hull City on Sunday.