The Comeback Player of the Year is perhaps the most nebulous award in all the NFL. There don't seem to be any hard or fast rules dictating exactly WHAT a player has to be coming back from in order to win the prize. Returning from injury is usually a good way to attract the voters attention. In 2018, Andrew Luck passed for 4,593 yards and 39 touchdowns, enough to earn him the award after missing the entire 2017 campaign.
But Philip Rivers wasn't injured in 2012, as he led the San Diego Chargers to a 7-9 record on the back of his 3,606 yards and 26 touchdowns.