The Vikings running back left Sunday's game against the Lions with an injured left knee after going down without contact.
On the other side of the ball, the Lions defense was able to hold Vikings quarterback Case Keenum to 219 passing yards, allowing him to complete just 16 of his 30 passes. Stefon Diggs had five catches for 98 yards.
So the loss to Detroit, while not pretty, is hardly as significant a blow as the possibility of being without Cook.More news: F1 Loses Out to Motorcycle Grand Prix in Malaysia
Cook was tended to on the field by trainers before walking off on his own power and back to the Vikings locker room with head team trainer Eric Sugarman. He was announced out shortly after.
Dalvin Cook's promising rookie season could be over.
Trailing 14-7, the Vikings drove to first-and-goal at the Detroit in the waning moments, looking for a chance to tie the game. Keenum's fourth-down pass was high out of the back of the end zone. He also recorded four quarterback hits and recovered a fumble.
Rookies Jarrad Davis and Kenny Golladay were on the inactive list, Davis for the second week in a row. WR Kenny Golladay, RB Dwayne Washington, S Don Carey, G Tim Lelito, RB Tion Green and LB Thurston Armbrister are also inactive for Detroit. On a cut to evade Lions safety Tavon Wilson, Cook reached down toward his left knee. Minnesota DE Danielle Hunter, who had 12.5 sacks last season, had his first two sacks of the season.