Cam Newton has been dealing with pain in his throwing shoulder. He has been throwing less downfield passes due to the pain, most notably in week 14 where he threw 4 interceptions against the Tampa Bay defense and was relieved by back-up Taylor Heinicke for a Hail Mary attempt.
This started in at the end of the 2016 season after he landed onto his shoulder during a tackle against San Diego. He was ultimately had rotator cuff surgery for a partial rotator cuff tear.
The rotator cuff is a band of tendon that connects the humerus (arm bone) to the shoulder girdle. It allows for rotation of the shoulder and the ability to pull the humerus above the head. Tears can be partial or complete and usually require surgery if it affects the throwing arm of an athelete, although it can be delayed until the season ends. Quarterbacks can expect to start throwing 12 weeks after surgery.
Cam Newton most likely has a partial tear in his shoulder that may be have been aggravated from a fall or from throwing the football. It is difficult to confidently tell even with an MRI how bad this injury is.
He will mostly likely play the rest of the season and post- season if he can and opt for surgery in the off season. This can range from a simple cleanup (after which he can throw after a few weeks) to re- repairing the tendon (which would be 12 weeks again), but he would be back before training camp in either scenario.
In the worst case scenario, although unlikely, we could be looking at an Andrew Luck- type situation long- term or potentially shutting him down for the rest of the season if the Panthers are totally eliminated from the post- season.