The 43-year-old announced that he will no longer compete in Formula 1 from the end of the season following a two-year stint with the German-based team.
"I think he's the greatest racing driver of this century," said Brawn. "Michael brought a lot to the team in this second period that people don't see.
"We haven't achieved what we wanted to together and that's frustrating, but what we do achieve in the future, Michael will have made a contribution to it."
McLaren driver Lewis Hamilton will replace Schumacher at Mercedes for their campaign next year.