Mertesacker was dropped for Arsenal's 2-0 win against Everton on Sunday after a horror show at the back in the 3-1 Champions League loss to Monaco.
January signing Gabriel replaced the World Cup winner against the Toffees and impressed as the Gunners kept their first clean sheet in the league since February 1.
When Gabriel first arrived at the club, Wenger spoke of his concern that his lack of English could make him a liability at the back.
But the Brazilian has looked assured in his three appearances so far and Wenger was quick to praise his performances.
"We bought him to play regularly and of course, that is the target for him," Wenger said.
"His English is not perfect yet. Yes, he understands more than he talks.
"He has shown that he is a defender who is committed, focused and can integrate well in our defensive style.
"Overall his first game was a very positive one."
