The Vikings placed cornerback Patrick Peterson on the COVID-19 reserve list on Monday, meaning they could be without another defensive starter on Sunday against the Lions.

Peterson said before the season he is vaccinated against COVID-19, so his placement on the reserve list suggests he tested positive for a breakthrough case of the virus. If he is asymptomatic, he can return with two negative tests taken at least 24 hours apart; if Peterson has symptoms, he would need two negative tests at least 24 hours apart and 48 hours without symptoms before he can come back. Otherwise, he would have to be away from the team for 10 days.

Coach Mike Zimmer, though, didn't sound optimistic Monday evening about the prospect of Peterson testing out of the COVID-19 protocol before Sunday's game.

"Not too many guys have passed those two negative tests, so you just have to let it play out and see where it goes," Zimmer said.

He missed three games with a hamstring injury before returning for the Vikings' win over the Packers on Nov. 21; Peterson played all 70 snaps in the team's loss to the 49ers on Sunday.

The Vikings played Sunday without their four preferred defensive linemen (Danielle Hunter and Michael Pierce are on injured reserve, Dalvin Tomlinson is on the COVID-19 list and Everson Griffen is away from the team while receiving mental health treatment). Tomlinson, who went on the COVID-19 list Nov. 23, could return in time for the Lions game, but in addition to the possibility of not having Peterson, the Vikings might be without Anthony Barr, who strained his hamstring during Sunday's game.

Zimmer said coaches have to go back to the drawing board as they adjust the plans amid personnel changes and allowing 400 yards in back-to-back games.

"We're going to have to put our heads together here a little bit this week and see how we can adjust," Zimmer said, "and change to do some of the things that these guys can do [well]."

Peterson is the 10th Vikings player to go on the COVID-19 list since the beginning of November; the team has since activated eight of those players, with Peterson and Tomlinson the only players currently on the list.

'I had my hand under it'

Receiver Adam Thielen said Monday he doesn't blame officials for not overturning what was ruled an incomplete pass from quarterback Kirk Cousinsin the fourth quarter against the 49ers. Thielen had no doubt he caught the pass, but that even he couldn't see on replay what he said he felt, which was his hand underneath the ball. According to Thielen, he was told the call on the field would've stood either way due to an inconclusive replay. The Vikings lost the challenge and a second-half timeout.

"They told me that if it would have been called a catch on the field, it would have stood," Thielen said. "But since it wasn't called a catch on the field, then it wasn't a catch. But I know for sure it was a catch. I had my hand under it; I could feel it. That's why I was so adamant on the sideline saying to challenge it."

A different 5-6?

The Vikings have just two defenders — safety Xavier Woods and linebacker Eric Kendricks — who have played every snap through 11 games this season. Attrition was the first reason Zimmer cited for why this 5-6 record is different than last year's 5-6 record. Five defenders have already missed at least two starts: Pierce, Barr, Hunter, Peterson and Harrison Smith. Their depth has not been adequate enough; they're allowing 25.1 points per game, ranking 24th in the league.

"I watch this team and they are different than last year," Zimmer said. "We've had a ton of injuries on the defensive side of the ball. I just feel like these guys continue to push and fight and our offense has pulled some games out. I don't think this is anything like last year. But we'll have to see when we play the last six weeks."