The Raiders placed Masterson (knee) on injured reserve Saturday.
Masterson popped up on the Raiders' injury report Wednesday with a knee injury, and he was ruled out ahead of Sunday's game against the Broncos. However, the knee injury appears to be severe enough to warrant a stint on injured reserve. The 26-year-old linebacker will be forced to sit for at least the next four games, meaning the earliest he can return is Week 9 against the Bengals on Nov. 3. Amari Gainer, Amari Burney and Tommy Eichenberg are candidates to slide into the starting linebacker spot vacated by Masterson.