Doctors fear that the disk is on the brink of being herniated, reports Mortensen. Offseason surgery is an option, though one the 33-year-old hopes to avoid. The injury first became a problem three weeks ago.
Rivers has received epidural injections, reports Mortensen, and missed his first practice since 2007 on Wednesday because of the injury.
He played in a win over the San Francisco 49ers on Saturday, throwing for 356 yards, four touchdowns and three interceptions. He has now thrown eight interceptions in his last five games.
On the season, Rivers has thrown for 3,995 yards, 31 touchdowns and 16 interceptions.
San Diego (9-6) plays the Kansas City Chiefs in their regular-season finale on Dec. 28.
- Molly Geary