Mahinmi doesn't have to be special. Mavs just need him to need be awful. Haywood only played 8 minutes in Game 2. Mavs went small for awhile and Cardinal played some. But if Mahinmi can survive 10 minutes without killing the team, then he's done his job.
That assumes that Chandler can stay out of foul trouble. I expect the Heat to drive on every possession, especially if Haywood can't play.