J.J. McCarthy’s availability for Week 13 appears to be up in the air after another rough outing Sunday.

Head coach Kevin O’Connell confirmed Monday that his struggling second-year quarterback is in the concussion protocol after reporting symptoms on the flight back to Minnesota following a 23-6 walloping in Green Bay, according to ESPN.

Max Brosmer, an undrafted rookie out of Minnesota, is the backup after veteran Carson Wentz underwent season-ending shoulder surgery earlier this fall.

It’s been a chaotic season at quarterback for the Vikings, who gave the keys to McCarthy after ex-Jets bust Sam Darnold departed for the Seahawks in free agency following a 14-3 career revival.

The 10th overall pick in the 2024 draft — who missed his entire rookie season after tearing a meniscus in preseason — has struggled under center, with this week’s lopsided defeat in Green Bay sounding even more alarm bells.

McCarthy completed 12 of 19 passes for just 87 yards, zero touchdowns and two interceptions. He was also sacked five times as the Vikings fell to 4-7 on the year.

“I’ve got to be better,” McCarthy said afterward. “I’ve got to do a lot of things better.”

Should McCarthy miss Sunday’s game — coincidentally enough against Darnold in Seattle — it would be the second time this season he’s sat out due to injury.

He missed a five-game stretch earlier in this season after sustaining a high-ankle sprain in Week 2, paving the way for Wentz to take the reins.

McCarthy has thrown six touchdowns and 10 interceptions across six games. He’s also rushed for two scores while completing 54.1 percent of his passes.

Kickoff is set for 4:05 p.m. Sunday.