Mitchell has received a number of fines for his play this season, the most recent of which came for taunting St Louis Rams quarterback Sam Bradford, leading him to claim that NFL commissioner Roger Goodell was unfairly targeting him.
Rivera refused to be drawn on whether he thought that Mitchell was being singled out by the league authorities, but he did praise the 26-year-old for what he had brought to his side's defence.
"Mike plays very hard, physical football. He has a great style, a great brand. It's spreading among our players in terms of being physical football players," Rivera told reporters.
"He's done a great job for us. I appreciate what he's doing for us as far as our defence is concerned."
The Panthers, who are on a three-match winning streak, will take on the Atlanta Falcons in an NFC South clash on Sunday.