Minnesota Vikings running back Dalvin Cook appeared to suffer a non-contact knee injury against the Detroit Lions when his leg buckled on a 10-yard run resulting in a fumble that was recovered by the defense.

The Vikings’ initial diagnosis for Cook is a nearly complete ACL tear, according to NFL Network’s Ian Rapoport. Cook will have an MRI on Monday.

Prior to the injury, Cook had 66 yards on 13 carries for the Vikings and the team’s only touchdown of the day so far. The second-round pick quickly ascended to a starting role with the team and tallied 288 yards and a touchdown in his first three games.

The Vikings waited just a few minutes to rule out Cook for the remainder of the game.

The rookie immediately held his left knee after the leg buckled and appeared to be in serious pain as trainers worked on it. He was spotted after the game on crutches, and the team’s staff is concerned he could have significant ligament damage.

What does this mean for the Vikings? The team has had some rough injury luck, but the question is what they have with Latavius Murray. The former Oakland Raiders running back was signed to a three-year, $15 million contract in the offseason but has been relegated to just a few touches per game with Cook taking over the workhorse role.

In the first three games of the season, Murray had just seven rushing attempts for 17 yards and hadn’t touched the ball once against the Lions prior to Cook’s departure.