Newton is recovering from a fractured rib sustained on Aug. 22. He's listed as questionable for Sunday's season opener, and Rivera said he will decide on Sunday whether or not Newton plays.
"There's some things you can't measure, and that's how he'll react when he gets hit. So when we make our decision Sunday morning it's going to be based on how we feel he's done the last couple of days, how he feels in terms of handling what we want to do with the game plan and whether or not we believe he'll be able to protect himself if he takes a shot.''
Newton, 25, threw for 3,379 yards, 24 touchdowns and 13 interceptions last season. Derek Anderson is listed as his backup.
The Panthers open the season at the Tampa Bay Buccaneers.
- Ben Estes