Dalvin Cook limped off the field and the Minnesota Vikings fear he may not get back on it this season.

The Vikings lost their top running back Sunday to what could be a torn knee ligament, which would end his rookie year.

Tennessee and Oakland finished losses without their starting quarterbacks, and the Atlanta Falcons lost their two leading receivers, but the most serious injury was Cook's.

He had 13 carries for 66 yards and a touchdown before his knee buckled on a third-quarter run and he went down and fumbled. Cook was scheduled for an MRI to determine the extent of the damage, but he was on crutches afterward with a bulky brace on the knee.

"I told him he's not the first great running back to have an ACL, if it is one, and come back pretty good," coach Mike Zimmer said. "Dalvin will have a great career."

He was having a good first season, entering the week ranked second in the league in rushing. He has 354 yards on 74 carries and two touchdowns.

"Dalvin's a really explosive player, and he has such good big-play ability," Zimmer said. "So we'll have to look at things differently. But if you lose a guy like him, you lose a lot of firepower."

The Falcons lost plenty of it when Julio Jones left in the second quarter with a hip flexor injury. Mohamed Sanu was then ruled out with a hamstring injury in the third quarter, and the defending NFC champions lost for the first time this season when the Buffalo Bills beat them 23-17.

Coach Dan Quinn said Jones, who was limited during practice this week with a lower back injury, wanted to return but could not have played with his usual explosiveness.

Falcons left tackle Jake Matthews said losing the team's top two receivers was no excuse.

"We know we're good enough to score even if we're missing a couple guys," Matthews said.

The Bills lost safety Colt Anderson to an arm injury in the first quarter, along with linebacker Ramon Humber (thumb), receiver Jordan Matthews (thumb), and cornerback E.J. Gaines (groin).

Marcus Mariota had two rushing touchdowns — the first Titans quarterback to do that in a game since Steve McNair in 2003 — but injured his hamstring and didn't play after halftime of the Tennessee's 57-14 loss in Houston. He will have an MRI on Monday.

The Raiders didn't have Derek Carr to try to lead them back in Denver after he was shaken up on sack in the third quarter of their 16-10 loss. He was sacked by Shelby Harris and was hit by Adam Gotsis as he twisted awkwardly. Coach Jack Del Rio said Carr suffered from back spasms.

Seattle starting running back Chris Carson sustained a left leg injury late in the Seahawks' 46-18 home victory over Indianapolis in the night game. Trainers immediately placed an air cast on Carson's leg and he was carted off the field. Coach Pete Carroll said Carson's injury was significant.

Devin Funchess caught a touchdown pass in Carolina's 33-30 victory at New England, but limped off late in the fourth quarter. Safety Kurt Coleman left in the second quarter with a knee injury and receiver Damiere Byrd departed with a forearm injury. The Patriots' Eric Rowe and Elandon Roberts left with groin injuries.

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