EAGAN, Minn. -- The Minnesota Vikings placed quarterback Kirk Cousins on the reserve/COVID-19 list on Friday, the team announced. Cousins, who is not vaccinated, will not be eligible to play at the Green Bay Packers on Sunday night.

Cousins was subjected to a daily testing cadence because of his vaccination status. He experienced symptoms on Friday and then tested positive for the virus, sources told ESPN's Adam Schefter. The Vikings activated backup quarterback Sean Mannion on Friday; he had been placed on the reserve/COVID-19 list hours before Minnesota's loss to the Los Angeles Rams in Week 16. Mannion, who is vaccinated, was "sick," according to coach Mike Zimmer.

"We hate to see that happen to Kirk, but he's done a lot of great things for us, and Sean is a really good football player and we're expecting him to go out and play really well," Zimmer said.

Mannion will start against the Packers. Minnesota signed Kyle Sloter -- who spent the 2021 season on Las Vegas' practice squad -- earlier this week while Mannion remained on the reserve/COVID-19 list. Rookie Kellen Mond, who was active for the first time all season against the Rams as Cousins' backup, rounds out the QB depth chart.

Despite Mannion not practicing in the week leading up to Minnesota's second meeting with its NFC North foe, Zimmer said there was not much consideration given to Mond starting over the veteran QB. The rookie was drafted in the third round in 2021 and has not appeared in a game this season.

"No, there really wasn't," Zimmer said. "We knew that Sean was coming back, and Sean is extremely bright, he studies like crazy, he's a great competitor. He's put in his time, he's earned this opportunity and I think he'll do great.

"Sean knows the game plan cold. Like I said, he's an extremely brilliant person. He puts in the work every single week like he's going to be the starter. And he is this week."

Packers coach Matt LaFleur, who helped coach Mannion while with the Rams, was quick to praise the passer.

"First of all, what a great person, great teammate," LaFleur said Friday. "He's got a big-time arm. He is going to do exactly what the coaches tell him. He is so reliable in that regard. I've got a lot of respect for him not only as a person but as a player."

Mannion, a career No. 2 quarterback, has started only two games over his seven-year NFL career: a Week 17 loss in 2017 to the San Francisco 49ers while a member of the Rams and a Week 17 loss to the Chicago Bears with Minnesota in 2019. In both instances, the Rams and Vikings had already locked up postseason bids and rested most of their starters.

If Mannion throws a touchdown pass against the Packers, it will be the first of his career.

Mannion spent the 2018-20 seasons in Minnesota as Cousins' No. 2 and was signed to the Vikings' practice squad in early September after spending training camp with Seattle Seahawks. He was then promoted to the active roster on Sept. 21.

The Vikings face a must-win situation in Green Bay to keep their playoff hopes alive. According to ESPN's Football Power Index, Minnesota's chances of making the playoffs increase to 46% with a win over the Packers and drop to 2% with a loss.

Zimmer said this week that the Vikings were taking more safety measures to keep Cousins and Mond separated to prevent COVID-19 from further affecting the quarterback room.

"We don't want those guys in the same room together, so we're going to try and spread them apart," Zimmer said.

Following a 30-23 loss to the Rams in Week 16, Cousins was asked about how the quarterback room would need to adjust with COVID-19 already in the Vikings' building.

"It just is what it is," Cousins said on Sunday. "At this point, you just have to follow the protocols, be disciplined and there's a lot of people not testing. So, it's in our building. It's going to be in our building. It's going to spread. We've just got to be disciplined to keep our distance and make sure that to the best of our ability we don't get it, but it is going to be difficult."

The Vikings had the first NFL quarterback room to be affected by COVID-19 this season after Mond tested positive for the virus during the first week of training camp. Both Cousins and former backup Nate Stanley were deemed high-risk close contacts and were forced to quarantine for five days before returning to practice.

During their night practice on July 31, the Vikings had only one quarterback available -- Jake Browning, who is now on the practice squad in Cincinnati.

After he returned to practice in August following his five-day isolation, Cousins said he was "at peace" with his vaccination decision and called it "a very private health matter."

At one point during the preseason, the Vikings had the highest percentage of unvaccinated players in the NFL. Zimmer aired his frustrations with all the unvaccinated players in Minnesota's locker room -- not just the quarterback group -- and warned of the situation that the Vikings now face.

"Something like this happens a day before a game that has a chance to get you to the playoffs or something like that ... this delta variant is rough," Zimmer said on July 31.

Two days later, Zimmer doubled down on his stance when asked how he would react if the Vikings lost a game because their starting quarterback or a star player was unavailable because of COVID-19 protocols.

"Probably won't be happy we lost the game, first, and I probably won't be happy we could've prevented this," the Vikings coach said on Aug. 2. "Like I said, these guys, some of them just won't do it. I shouldn't say it, but some of the things they read is just, whew, out there."

Cousins is not the Vikings' only star player to end up on the reserve/COVID-19 list. Safety Harrison Smith missed two games after testing positive the morning before a loss to the Baltimore Ravens, and running back Dalvin Cook missed last week's loss to the Rams after testing positive. Starting nose tackle Dalvin Tomlinson was also out 10 days after being placed onto the reserve/COVID-19 list.

Information from ESPN's Rob Demovsky was used in this report.