EDEN PRAIRIE, Minn. (AP) — Dalvin Cook became the latest integral offensive player lost by the bad-luck-trodden Minnesota Vikings.

The team’s fear of a torn ACL in the rookie running back’s left knee was realized Monday, sealing the end of a promising rookie season.

Coach Mike Zimmer confirmed the diagnosis, signaling the switch to Latavius Murray as the primary ball carrier. Cook will have reconstructive surgery once the swelling subsides. Some additional cartilage damage was discovered, Zimmer said, but no additional ligaments were injured beyond the ACL.

“He’s a great kid,” Zimmer said. “I’m extremely impressed with everything he’s done to this point. It’s obviously a terrible thing for him, and for us, but we’ll move forward and go on from there. He’s a great worker, and I have no doubt that he’ll come back from this.”

Cook was injured trying to cut for more yards near the end of a run in the third quarter of Minnesota’s defeat by Detroit on Sunday . He lost a fumble on the play and needed help off the field. Afterward, he was on crutches, wearing a bulky brace.

“I’m praying for him,” Murray said. “I told him I care about him, more than anything, that he’s all right.”

Cook endured some shoulder trouble in college at Florida State, but this will be a new challenge.