The Carolina Panthers just haven't been the same since Wade Phillips blitzed the smirk right off Cam Newton's face in Denver's Super Bowl 50 upset 22 months ago.

Before that game, the Panthers of 2015 were a charmed 17-1 with a league-trouncing turnover ratio of plus-28. Since that game kicked off, however, Superman has gone 14-13 with 31 turnovers. His team is 14-15 with a turnover ratio of minus-10.

The Panthers went 6-10 last season to become the 15th Super Bowl loser to miss the playoffs the following season. Then Newton missed the entire offseason because of surgery on his passing shoulder. What's followed has been one of the stranger 12-game stretches you'll find for a team that's 8-4 and sitting in the sixth and final NFC playoff spot heading into Sunday's game against the Vikings at Bank of America Stadium.

"It's been kind of a strange set of circumstances," Panthers coach Ron Rivera said. "We didn't have a full training camp with our quarterback. He's kind of had to work himself back into football shape. It's been a challenge, but our guys have responded and done some good things."

The Panthers started 2-0 by allowing only a field goal in each win. Then they gave up 34 points in a loss.

The Panthers beat Tom Brady in a shootout at New England. Three weeks later, they lost 17-3 to Mitch Trubisky in Chicago. Mitch completed four passes and the Bears mustered five first downs, but Cam turned the ball over three times.

A week after they lost 17-3, the Panthers won 17-3 at Tampa Bay.

That started a four-game winning streak. But even that stretch looked unsteady. In a 35-27 win at the Jets, the Panthers needed fourth-quarter touchdowns from their defense and special teams to cover for Newton, who completed 11 of 28 passes for 168 yards.

"I always hear often that it was an ugly win, but I never heard of saying such thing as a pretty loss," Newton said after the game. "So either way it goes, we would prefer to get a win at the end of the day — great team win. … We're not going to apologize for that."

Newton, the league MVP just two years ago, ranks 25th in passer rating (83.0). He's barely completing 60 percent of his passes (60.5), and only four players have thrown more interceptions than the 11 he's tossed.

And now he's heading toward a Vikings defense that sacked him eight times while holding him to 10 points in a beatdown at home last season.

"I think everybody has their little ups and downs a little bit," Vikings coach Mike Zimmer said. "I see the things that he does really good, and that's what we try to defend.

"He throws the ball great down the field. He moves in the pocket well. He runs good. On the move, he throws well. I don't know. I can't tell you about [his struggles]. I just know the guy that went to the Super Bowl a couple years ago."

Defensively, the Panthers rank sixth overall, fourth against the run and fourth in sacks per pass play. And, oh yeah, in four of their eight wins, they've not allowed an offensive touchdown.

But …

Through Week 13, their 11 takeaways ranked ahead of only Oakland (nine) and Atlanta (10). And their five defensive interceptions ranked ahead of only Oakland (one) and Atlanta (three).

"It's a case of missed opportunities," Rivera said. "I bet if we go back through it, we got seven or eight dropped interceptions we should have had this year. Go back to last year, I think it was nine. I think that's part of it. When you have a chance to make plays, you got to make plays."

During that charmed 17-1 run to Super Bowl 50, the Panthers had an incredible 48 takeaways. So Superman isn't the only one who just doesn't look quite the same since old Wade blew things up 22 months ago.

Mark Craig is an NFL and Vikings Insider. Twitter: @markcraigNFL

E-mail: mcraig@startribune.com