— Jim Wyatt (@jwyattsports) September 16, 2012
Mathews has been out since San Diego's preseason game against the Green Bay Packers on Aug. 9. He has yet to practice as he recovers from a broken collarbone. In Week 1, Curtis Brinkley and Ronnie Brown combined for just 17 yards on 15 carries in his absence.
Gates, meanwhile, is a late scratch for the Chargers. He suited up in San Diego's win against the Raiders and recorded 4 catches for 43 yards. He left the game with a rib injury, but later returned.
Gates missed practice for most of the week, but made it back to the field on Friday and was considered questionable before this announcement.