Vikings star Dalvin Cook can't play against Rams after testing positive for COVID

As the NFL loosens testing requirements on vaccinated players, the Vikings — a locker room that entered the season with one of the league's lowest vaccination rates — will be without another key player on Sunday due to COVID-19.

Running back Dalvin Cook will not play against the Rams, according to coordinator Klint Kubiak, after being placed on the reserve/COVID-19 list before Thursday's practice. Receiver Justin Jefferson said he spoke with Cook on Thursday morning and that his spirits are "good" after testing positive.

Cook had been following protocols for unvaccinated players this season, and the Vikings ruling him out three days before kickoff indicates he remains unvaccinated — a status that still requires daily testing under new league protocols. If unvaccinated, Cook is automatically out Sunday and for a minimum of 10 days. Vaccinated players who test positive can return within 48 hours if they produce two negative tests.

Running back Alexander Mattison will start his fourth game of the season against Los Angeles, with rookie Kene Nwangwu backing him up.

"Big challenge not having Dalvin," Kubiak said. "Obviously, a team captain and great player. Unfortunately, he won't be available. But we've been through this this year already, and guys have stepped up. Alex has stepped up, Kene is getting more comfortable."

A 10-day isolation means Cook must be away from the team until at least Jan. 1 — a day before the Vikings' Jan. 2 game at Lambeau Field.

"It's COVID, you can't really do too, too much," Jefferson said. "He's been doing everything he was asked to do, protocols and everything, wearing his mask, staying away from people."

The NFL recently updated COVID protocols, rolling back testing frequency for vaccinated players. They're no longer tested weekly, instead undergoing daily symptom screening and random "spot" testing. That further incentivizes vaccinations for competitive advantage purposes, as less testing could turn up fewer positive cases and absences.

The Vikings' unvaccinated players this season have included Cook, quarterback Kirk Cousins, receiver Adam Thielen and safety Harrison Smith, among others. If they're still unvaccinated, they're being tested daily. Thielen and Smith have previously tested positive.

"You never know what's going to happen tomorrow, so we just have to make sure that we're prepared with the guys that are here," cornerback Patrick Peterson said. "Like in a situation with what happened today. We have to make sure Mattison was getting the looks he needed."

Cook and practice squad cornerback Tye Smith, also placed on the COVID list Thursday, are the Vikings' 17th and 18th players isolated since Nov. 4. Cook is the fifth starter to miss a game due to a positive COVID test this season; at least two, center Garrett Bradbury and Peterson, were vaccinated.

"You're conditioned by this point in the season to deal with these curveballs," Kubiak said. "Players and coaches, it's nothing we haven't seen before. The whole league is dealing with it. Games are going to get played. We've got a lot of guys with a lot of experience that can pick up the torch."

The Vikings re-signed running back A.J. Rose, an undrafted rookie, to the practice squad. Receiver Dan Chisena returned to practice Thursday after an 11-day quarantine. Practice squad guard Kyle Hinton also was cleared to return.

Cook's absence is a tough blow to a Vikings offense trying to get back on track. Cousins is on an injury report for the first time since 2013, dealing with a rib injury, after taking a season-high four sacks in Monday night's win at Chicago.

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They're coming off a season-low 193 yards against the Bears, and will have to jumpstart the offense without Cook, whose 1,288 yards from scrimmage ranks fifth among NFL running backs.

Mattison was cleared to return this week from a 10-day quarantine and positive COVID test. He has already started three games for Cook, who has dealt with ankle and shoulder injuries, and ran for at least 90 yards in each.

Receiver Adam Thielen hopes to give them a boost, but whether he returns three weeks after suffering a high-ankle sprain remains to be seen. He was limited again in practice. The Vikings also may be without offensive lineman Mason Cole, who remains sidelined by an elbow injury, meaning Oli Udoh could return to his spot at right guard against the Rams. Fullback C.J. Ham was held out of Thursday's practice due to a hamstring injury.

"The other backs that we have are going to do a great job replacing [Cook]," Jefferson said. "We just know as receivers that we've got to step up a little bit more. We've got to make those plays, those one-on-one balls."