Old friends and former Bears teammates Ron Rivera and Leslie Frazier stood on opposite sidelines inside the Metrodome on Oct. 13, 2013.

“Yeah, I remember that game,” said Vikings cornerback Captain Munnerlyn, who was with the Panthers at the time. “They were talking about firing Coach Rivera if we lost that game.”

No one ever really knows who “they” are. But some of those “theys” were saying the same thing about Frazier up here in the Twin Cities.

Both teams were 1-3. The Vikings had tipped their hand on Frazier before the season when they only picked up the one-year option in his contract rather than extend it. Rivera was signed through 2014, but his early-season struggles had grown old after he started 1-5 as a rookie head coach in 2011 and 1-6 in 2012.

“And we had a new general manager [Dave Gettleman],” Munnerlyn said. “We knew we had to go and turn the season around for Rivera. Guys in that locker room play for that coach. They play for him real hard. They know he’s a fighter and worked his tail off to get that position. I really think that game changed his career.”

That sounds extreme, but the numbers do suggest something began to move in the right direction that day. At least for Rivera.

Starting with that 35-10 win over the Vikings, Rivera has gone 30-11-1, collected back-to-back NFC South titles, won a playoff game and signed a three-year, $15 million extension. Frazier finished that season 5-10-1, was fired and is in his second season as Tampa Bay’s defensive coordinator.

As for starting fast, Rivera seems to have gotten the hang of that as well. The Panthers are 11-0 and became the NFL’s last undefeated team when the Patriots lost at Denver on Sunday night.

“I follow those guys every game,” said Munnerlyn, who played five seasons in Carolina as a 2009 seventh-round draft pick. “And I talk every week to Thomas Davis, Luke Kuechly, Ted Ginn. I was there so long and I stay there in the offseason.”

Carolina’s blueprint looks and sounds similar to what the Vikings began building around coach Mike Zimmer about the same time Rivera got his contract extension in early 2014.

“They’re playing great defense, and Cam [Newton] is protecting the ball,” Munnerlyn said. “He’s doing what they have to do to win. Protect the ball, don’t turn it over and make plays when they’re there.”

The Vikings are 8-3 and also lead their division. Their program isn’t as far along as Carolina’s, but it’s possible that only time and the evolution of quarterback Teddy Bridgewater and Zimmer’s defensive scheme are needed to make the biggest differences disappear.

Newton, obviously, is a much different quarterback. He has 427 yards rushing and a team-high seven rushing touchdowns. But Bridgewater can run and does have a higher average per carry (4.6-4.4), albeit on 64 fewer carries.

As passers, Newton and Bridgewater rank 19th and 22nd, with passer ratings of 89.5 and 85.4. Newton, who has a three-year head start on his career, is completing just 57.2 percent of his passes with 20 touchdowns, while Bridgewater is completing 65.2 percent with eight touchdowns.

Both know how to protect the football under a team concept built around running the ball, defense and favorable field position. The Vikings rank third in rushing attempts (331) and are tied for fourth in fewest turnovers (11). The Panthers rank first in rushing attempts (379) and are tied for seventh in fewest turnovers (12).

Defensively, Carolina is lapping the field in takeaways with league highs in total takeaways (28), interceptions (18) and turnover differential (plus-16). The Vikings have 14 takeaways and are plus-3.

“We might see those guys someday,” Munnerlyn said. “I think we all know the world goes through Charlotte for the Super Bowl this year.”

Munnerlyn has made his respect and admiration for Zimmer well known, especially since the slightly bullheaded cornerback started accepting Zimmer’s teaching this year. His feelings toward Rivera are similar but in a different way.

“He played [linebacker] on one of the best defenses to ever play this game, the ’85 Bears,” Munnerlyn said. “He’s a players’ coach and a great guy. I always mess with him every time I see him. I say, ‘Hey, when things got serious [in 2013], we helped you get that big contract you got.’ ”