The team is concerned that Hoyer tore his ACL but will not know for sure until he undergoes an MRI on Friday at the Cleveland Clinic, a league source told ESPN's Adam Schefter. After the game, Hoyer was on crutches with his right knee immobilized. He was putting weight only on his left leg.
Hoyer's quick ascension to the starting job with the Browns may be derailed by what could be a serious knee injury.
"It's serious enough that we'll get an MRI on it," coach Rob Chudzinski said.
That's as far as he would go.
"I don't want to be premature," Chudzinski said. "Let's find out what the status is and see what the MRI says. Anytime you lose a guy who's done what he's done, it's disappointing. But let's see what the MRI says."
Hoyer was injured at the 3:57 mark when he was hit by Bills linebacker Kiko Alonso as Hoyer went to slide. Alonso's momentum took him over Hoyer's chest, and Hoyer's knees were caught awkwardly underneath him. The quarterback immediately rolled over, his face expressing pain.
Hoyer had gone from third team to starter after Brandon Weeden sprained his thumb. In two starts, Hoyer led the Browns to wins over the Minnesota Vikings and Cincinnati Bengals. More importantly, he brought positive vibes and energy to a team that needed it, completing 60 percent of his passes and throwing for five touchdowns.
"It's never good to see your quarterback go down in that fashion," tight end Jordan Cameron said.
"It's tough," said left tackle Joe Thomas. "You don't plan for it."
If Hoyer is out, the Browns will again turn to Weeden, who threw for 197 yards and a touchdown in Thursday's win. Weeden said he visited with Hoyer at halftime to try to offer encouragement.
"You hate to see it," Weeden said. "You hate to see it because he's a teammate, a friend, and he was helping this team win. I just tried to be as positive as I could, and he was in there celebrating when we won."
The Browns reported one other significant injury, saying defensive tackle Desmond Bryant was taken to a hospital with shortness of breath. Chudzinski had few details other than Bryant had no previous breathing issues while with the team.
"We took him for further evaluation," Chudzinski said. "I don't have any more information on that right now."
Also, running back Chris Ogbonnaya left the game because of a concussion.