Bills quarterback Kelly Holcomb left the game with a severe concussion against Kansas City, while Bears running back Cedric Benson sprained his knee against San Francisco.
Coach Mike Mularkey said he wasn't sure whether Holcomb would be able to start next week against San Diego, and Benson is scheduled to undergo an MRI exam today.
Holcomb was hurt in the second quarter of a 14-3 win when he was sacked by Jared Allen. Holcomb fell backward and landed on teammate Mike Williams' leg, forcing the quarterback's head to snap back. He was on the field for a few minutes and looked groggy while trainers attended to him on the sideline.
J.P. Losman took over, producing two touchdown drives in his first appearance since Holcomb was named starter following a 19-7 loss to New Orleans on Oct. 2.
Buffalo also lost starting free safety Troy Vincent, who hurt his shoulder in the second quarter and didn't return. Without providing the severity of the injury, Mularkey said Vincent will be re-evaluated through the week.
The Chiefs reported injuries to three players, who all finished the game: DE Eric Hicks (sprained left knee), WR Dante Hall (bruised left knee) and DE Carlos Hall (bruised right thigh).
Benson was taken off the field on a cart in the second quarter of his first NFL start. As he was being hit for a 2-yard loss by San Francisco's Isaac Sopoaga, Benson's right leg twisted under him.
49ers safety Tony Parrish also broke his left leg and ankle in the game.
"We don't really know yet," said Benson, wearing a brace as he stood in front of his locker. "They don't know what's torn, or if it's just strained."
Benson said X-rays were negative, but his knee was sore.
Benson had broken off an 18-yard run earlier in the series, and he left the game with 50 yards on 12 attempts in a 17-9 victory.
"I was off to a good day," he said. "That's an amazing offensive line. They can march it down the field on a consistent basis, avoid negative plays."
Benson started Sunday in place of leading rusher Thomas Jones, who was inactive with sore ribs.
Benson, the No. 4 pick in last April's draft, left Texas as the sixth leading rusher in NCAA Division I-A history with 5,540 yards. He held out of training camp in a contract dispute and did not play in the preseason, but had run well as a backup in the previous two games.
In an unusual injury, Vikings coach Mike Tice sprained or tore his MCL when he got knocked over on the sideline by a Giants player during Minnesota's game in New York.
"Fourteen years in the league and I never hurt my knee," he said with a chuckle. "I guess I was turning and yelling at somebody."
In Miami, Patriots running back Corey Dillon was limited to two plays because his leg tightened. Center Dan Koppen also went to the locker room in the third quarter with a left arm injury.
Jets right tackle Jason Fabini tore his left pectoral muscle against the Carolina Panthers and is out for the year.
In Detroit, Cardinals OG Reggie Wells (ankle), LB Karlos Dansby (groin), TE Eric Edwards (head) and Detroit LBs Boss Bailey (ankle) and Earl Holmes (knee) left the game with injuries.
Jaguars WR Ernest Wilford sprained his right shoulder in the fourth quarter in a 30-3 win over Baltimore, and Bucs DE Greg Spires sprained his left shoulder in a win over Washington.
Steelers leading rusher Willie Parker was held out of Pittsburgh's game against Cleveland with a sprained ankle, and Duce Staley got the start. Browns cornerback Daylon McCutcheon sustained an abdominal injury while colliding with Steelers wide receiver Hines Ward and was taken off the field on a cart midway through the first quarter.