Both starting quarterbacks left the NFL's Thursday night game with right knee injuries.
The Cleveland Browns' Brian Hoyer came out in the first quarter, and the NFL Network reported the team feared he tore knee ligaments. Hoyer was headed for an MRI exam.
In the third quarter, Buffalo Bills rookie quarterback EJ Manuel left the game.
Hoyer was attempting to escape pressure and run for a first down when his legs bent awkwardly underneath him while he was tackled by Bills linebacker Kiko Alonso. Hoyer was helped off the field and then walked to the locker room without assistance.
Brandon Weeden, who began the season as the starting quarterback, replaced Hoyer and drew boos from the crowd.
Manuel was hurt on a hit by Tashaun Gipson. Undrafted rookie Jeff Tuel, who posted a 4-22 record as a starter at Washington State, replaced Manuel for the Bills.
During the preseason, Manuel underwent surgery on his left knee.