The criticism comes from Cincinnati Bengals defensive coordinator Mike Zimmer, who was with the Falcons when Petrino was the head coach back in 2007.
Zimmer returns to Atlanta this weekend for the first time since then. He told reporters in Cincinnati on Wednesday that Petrino was a coward for quitting the Falcons with three games left in the team's season. He called Petrino "gutless."
Zimmer said, "Most people in football have enough courage about them and enough fight to stick through something and not quit halfway through a year. It is cowardly."
At practice Thursday, Petrino declined to comment on Zimmer's statement.
"I just focus on our football team and what we've got to do Saturday," he said. "I'm real excited with the football team we have. I love coaching this team."