Jack Del Rio said on Monday that starting quarterback Derek Carr has a fracture in his back following a sack in the Raiders loss in Denver.
Carr is set to miss 2-6 weeks with the injury meaning that back up quarterback EJ Manuel is set to start for the interim in Oakland.
Manuel was a former first round pick by Buffalo in 2013 and started in 28 games in four seasons with the Bills.
The former 16th overall selection is 6-11 in 17 career starts in the NFL. His last start was week 17 for Buffalo in New York against the Jets.
Manuel was eventually benched in the game and replaced by Cardale Jones.
The Bills host the Raiders in four weeks at New Era Field