The Bills are jokingly called "Panthers North" by some on social media, but a quick history lesson for those who don't remember -- the connection began more than 20 years ago, in the other direction.
Former Bills GM Bill Polian was Carolina's first general manager in 1995, and immediately signed former Bills players Don Beebe, Carlton Bailey, Frank Reich and Pete Metzelaars.
So Carolina might actually be "Bills South." Semantics.
Either way, there's a reason front-office decision-makers and coaches bring in players they have worked with previously. Especially during the regular season, but even during the latter parts of the preseason, players' ability to quickly adapt weighs heavily into the decision to sign them.
It's why Beane signed Coleman after former Bills safety Rafael Bush announced his retirement days before training camp began in July. It's also why Beane signed Munnerlyn on Saturday after placing cornerback E.J. Gaines on injured reserve with a groin injury.
Coleman and Munnerlyn played under McDermott when he was Carolina's defensive coordinator. With that level of familiarity, the idea is for both players to pick up where they left off, with minimal acclimating needed.
"We're getting to the point where we've got to start finalizing who's going to be on our final roster," Beane told ESPN after the team's practice Sunday. "A guy like Captain ... it's a cleaner fit right in [to the system]. I just talked to him after practice and he said, 'There's only a few checks that are different, everything else is exactly what I know.'
"It's like plug-and-play versus getting someone up to speed."
Munnerlyn practiced with the Bills for the first time Sunday -- his first football activity since the Panthers released him in February.
The 2009 seventh-round pick suited up, but mostly observed when the Bills ran team drills. As he took in a bevy of new information, he realized a lot of that information was already in his head.
"I was sitting there like, 'Wow, I remember this,'" he said. "This is simple for me because I've been in this system for seven years of my career.
"It's definitely like riding a bike for me, especially being with Coach McDermott, who knows me, knows the type of player I am and what I bring to the table. I played my best football under him, so hopefully, I can get back to that form."
Munnerlyn played under McDermott from 2011 through 2013, increasing his total tackles each season and returning all four of his interceptions for touchdowns as a full-time starter. He signed with the Minnesota Vikings in 2014 but returned to Carolina in 2017.
His second stint with the Panthers was not as statistically successful as his first, ultimately leading to his release as part of the team's desire to get faster and younger on defense.
As excited as he was to reunite with McDermott, Beane, Coleman and Lotulelei, Munnerlyn looks forward to seeing his former teammates in South Carolina this week, where the Panthers are playing host to the Bills for joint practices before their preseason game Friday.
He didn't display any animosity toward the organization that drafted him -- other than a lighthearted "guarantee" that they'll hear about it whenever he makes plays -- but it's clear the way he left Carolina doesn't sit well with him.
"It was disappointing because that was my first time in my career [being released]," he said. "I've always played my contracts out. ... It was disappointing because I felt like I still could've helped those guys out a lot. I'm young still, I've got a lot of football left in me."
Munnerlyn is not as quick as he was when he entered the league -- few players are. But after 10 years in the NFL, he's only 31 and far from decrepit.
That experience worked in Munnerlyn's favor, as the Bills valued savvy during their most recent venture into the free-agent pool.
"Sometimes a guy who maybe doesn't have the same athletic genes he had five or six years ago, but still can play and knows everything is better than a guy who's maybe younger but still learning the game and has no idea how to play in this defense," Beane said. "How long will it take them? Is it two weeks, is it a month? ... Guys like Captain and Kurt Coleman -- those guys can come right in and play.
"They still have to have the ability, they still have to show what they can do, they still have to earn a spot. But the mental part of it, they already check that box."
Munnerlyn might not start over Taron Johnson or Siran Neal at nickel corner, but Buffalo doesn't necessarily need him to. He'll be a veteran presence in a cornerbacks room where, with Gaines out, no other player has more than 40 games of NFL experience.
His addition also offers a rare moment of sentimental value in an often ruthlessly businesslike league.
"We've stayed in touch and in this job, players come and go, coaches come and go -- and that's the hard part of the job," McDermott said. "The satisfying parts of the job are moments like that where you can stay in touch with players. ...
"It's neat that now we are with Kurt [Coleman] and some of the other players. It doesn't always happen for it to come back full circle to where we can work together again but it's satisfying."