If things had turned out differently, the mention of Bill Belichick could be a sore subject for Pete Carroll. After all, Carroll was fired 20 years ago by the New England Patriots so they could replace him with Belichick, the second time Carroll was fired by an NFL team in five years.

Instead, that decision by the Patriots—and let's face it, it turned out pretty well on their end—became a turning point in Carroll's career, paving the way for him to not just someday get another NFL job, but to become one of the league's most successful coaches.

And now, 20 years after Belichick replaced Carroll, the two will face off for the fourth time as coaches of the Patriots and Seahawks, and they'll do so not just as two of the league's longest-tenured coaches, but also representing the oldest combined age of opposing head coaches in an NFL game in league history, per NFL research.

"The fact that we're still coaching and our paths are still crossing, I guess that means we've done pretty well or somebody would have replaced us," Belichick said on a conference call with Seattle-area reporters this week. "I have a ton of respect for all that Pete's accomplished, both at Seattle and at USC and at other places in his career. He's a great coach."

As Belichick referenced, Carroll ended up at USC after being fired by New England, but an important part of that story is the year he took off between those jobs, using that time to more clearly define his philosophy.

When he was introduced as Seattle's head coach in 2010, Carroll said of his previous NFL jobs, "I didn't know who the heck I was as a football coach." Losing an NFL head coaching job—again—forced Carroll to regroup and made him a better coach, one who would not just get another crack at the NFL, but who would use it to become, after Belichick, the most successful coach of the past decade, winning one Super Bowl, leading the Seahawks to two, and reaching the playoffs eight times in 10 seasons.

"It was a crucial year for me," Carroll said in 2015 prior to coaching against his former team in Super Bowl XLIX. "… It gave me an opportunity to really collect my thoughts about moving forward and to get pointed in the direction that, really, we have maintained since. I had a tremendous opportunity to reflect on the time that I had had. It's such a whirlwind when you're coaching and you're flying so fast that sometimes, we don't figure out that we need to step back and revisit all of the stuff that's important to us. That's what happened, and out of that came every word of our approach and every philosophy that we stand by now.

"I didn't regret anything that happened at New England. It needed to happen for me to get to the point where I had to dig in and figure out what was right, so I'm proud of the way that process went because it really worked out."

And while Carroll and Belichick might seem like opposites, personality wise, it's their similarities, from their defensive backgrounds the disciplined way they run their programs, which in turn leads to consistency, that have made them to of the best at their profession.

"I think what's similar is our defensive background," Carroll said. "We've both been defensive guys our whole life, and we look at the game from that perspective I think in general. We both had the opportunity to be involved in our offenses a lot over the years. We've tried to—I know he does, I know I do—try to influence what we do on offense, how we do it. We both have really I think strong commitments to our approach and philosophy; it doesn't really matter much what happens, we're going to be pretty much the same with who we are, what we want to get done with our teams. I know that he is, and I know that I am, very fundamental coaches in this game as far as the tactical part of it, the technical part of it, the principles of playing good ball, executing, not giving your opponent much. We're both real committed in that sense. I think it's kind of a general football outlook. The two of us, the two teams, have really played similar in a lot of areas in terms of big numbers and stuff, turnovers, winning games, divisions, stuff like that. They've been way ahead of us with a lot more wins than us, but we're out there kind of. So there's been some similarities in the consistency."

The consistency shows up in the repeat playoff appearances for both teams, and there's no bigger indicator of both coaches' commitment to fundamentals than the fact that, since Carroll's second year in Seattle, New England ranks first in turnover differential over that nine-year stretch, and the Seahawks rank second, with a pretty significant gap between them and the No. 3 team on the list.

Lawyer Milloy, who played for both coaches in New England and for Carroll in Seattle for the final two years of his career, sees more similarities than differences between the two.

"They might seem different, but they're very similar," Milloy said before the two teams met in Super Bowl XLIX. "They're going to compete to get that locker room atmosphere right. Individuals are not bigger than the process. If you do anything to sway the direction of the team in the wrong way, you're out of there. Everybody thinks Pete is a happy-go-lucky player's coach or whatever, but look at his first year when we had (284) transactions. Everybody says he's a player's coach, but all the players were coming in every day looking to see if their name was still on the roster.

"The biggest difference is one's got a smile on his face, the other one doesn't, but the ultimate goal is to win championships, and both love, love winning. To be a good head coach, you've got to be a tremendous facilitator to build the right atmosphere; both those guys do that."

Belichick has long been complimentary of Carroll's talents as a coach, and singled out the 2016 meeting between the two teams as good example of what makes Carroll such a good coach. In Week 10 of that season, the eventually Super Bowl champion Patriots were coming off a bye and hosting the Seahawks on Sunday Night Football, while the Seahawks had to fly across the country on a short week, having played on Monday in Week 9, but Seattle still handed the Patriots one of their only two losses of the year, a 31-24 thriller that was one of the most impressive regular-season wins of the Carroll/John Schneider era.

"I have a ton of respect for Pete," Belichick said. "His consistency, his record, his ability to handle whatever comes, and do it in a way that doesn't distract the team—injuries and whatever things that we all deal with from time to time, but he does a great job of handling and keeping the team focused. They go out there and play hard play competitive every week, it doesn't matter where it is or who it is or what the circumstances are. They came in here and handled us in 2016. It was a great football game, it was as competitive of a game as I think as we've ever played in this stadium. We've played a lot of them, a lot of big ones, but that was a great football game—two evenly matched teams and they got the better of us. That's the type of effort you get from Pete and the Seahawks."

Considering the Patriots have hosted seven AFC Championship games during Belichick's tenure, calling that "as competitive of a game" as they've played in their home stadium is awfully high praise.

Twenty years ago, Carroll facing Belichick in the NFL in 2020 might have seemed like a long shot, both because not many coaches last this long, and because Carroll's getting another shot at an NFL job was anything but a given. But on Sunday the two coaches who hold each other in such high regard will go at it once again, and in all likelihood it will be another competitive, hard fought game—dating back to 2012, the previous three meetings between the two have been decided by a total of 12 points. And both coaches can take pride in knowing that, 20 years ago, a coaching changed in New England helped spark to wildly successful and lengthy careers.

"I do take pride in it, because it's hard to hold these jobs," Carroll said. "I know I've been fired a couple times. Again, I just think it's a statement of our commitment to the game years ago, and all the guys we worked with that taught us the principles of it, because you can't sustain this long and be consistent and win a lot of games for this long unless you got your act together in your game, in how you play this game, how it works and all. Neither one of us are fly-by-night guys. There's a real fundamental connection that we were raised right by the people we grew up under. But I do think also, it's a lot easier to stay with it when you win. It's hard if you get your butt kicked week in, week out, it's hard to hold onto your jobs and these opportunities. So I think it's all been a part of everybody that we've worked with, the organizations, coaches all that, that have given us a chance to find success and keep coming back."