Philip Rivers is officially questionable to play against the Buffalo Bills. The Los Angeles Chargers quarterback remains in concussion protocol ahead of Sunday's AFC matchup. Rivers has fully participated in practice the past two days after being limited on Wednesday. The veteran quarterback must be cleared by an independent neurologist before he's allowed to play again. The 35-year-old hasn't missed a game since taking over the Chargers' starting role from Drew Brees in 2006.