Browns rookie quarterback Brandon Weeden sustained a concussion in the final minutes of Cleveland's win over the Pittsburgh Steelers on Sunday.
He banged his head while falling awkwardly after an incompletion. Backup Colt McCoy, who suffered a concussion when the teams met late last season, came in and finished off the win without attempting a pass.
Coach Pat Shurmur said he spoke with the 29-year-old Weeden after the game.
"He's good," Shurmur said. "We had a good conversation. He's being treated for a concussion, and we'll see where that goes. Some guys come back quickly, some guys don't."
In Chicago, Bears receiver and return specialist Devin Hester left the game against the Minnesota Vikings with a concussion, and running back Matt Forte hobbled off midway through the third quarter with an ankle injury.
Colts rookie wide receiver T.Y. Hilton took a vicious high-low combination hit on his second punt and was left his head with both hands as he was motionless on the ground for several minutes.
A few minutes later, Hilton was cheered as he walked off gingerly under his own power. Team officials announced he was being evaluated for a head injury.
Hilton had already returned a punt for a touchdown. He returned later in the first half and helped Indy's sluggish offence wake up on the way to a win over the Bills.
Niners officials said Williams had a knee injury, while Hunter hurt his ankle and was questionable. The club did not specify which leg was hurt for either player.
Both were helped off the field and were soon taken by cart to the locker room. They were injured on a running play in which Hunter carried the ball for a 2-yard gain late in the third quarter.