In the list of names associated with the Patriots’ unprecedented run of success, Devin McCourty’s is rarely one of the first mentioned. Even moving beyond Bill Belichick, Tom Brady, and all of the players who have filled key roles on offense, the defenders who usually come up first are guys like Vince Wilfork, who was with New England from 2004–14, or young stars like Dont’a Hightower and Malcolm Butler. In a way, that’s part of what makes McCourty so emblematic of the franchise’s ideals. He does his job quietly, but few have had a greater impact on the Pats’ stretch of dominance.

Earlier this week, special teams ace Matthew Slater told the Boston Herald, “To me, in my mind, Devin is Mr. Patriot.” When it comes to the defensive side of the ball, he may be right. McCourty and end Rob Ninkovich are the longest-tenured members of the Pats defense. Together, they’re the only players who have been part of the New England unit since 2010 (Ninkovich’s first season starting with the team and the year that the Patriots drafted McCourty no. 27 overall).

McCourty came to the team as a prized cornerback, and that’s the spot he handled for most of his first two seasons in Belichick’s defense. He was every bit the cover man the Pats hoped he would be. McCourty went to the Pro Bowl as a rookie, and he was remarkably consistent during his time on the outside, a receiver-stifling robot in the mold that Belichick adores.

For most of McCourty’s early days in New England, though, the Patriots’ safety situation was a mess. Among Brandon Meriweather, Patrick Chung, and James Sanders, New England struggled to find answers at the position. So when the team traded with Tampa Bay for Aqib Talib midway through the 2012 campaign, Belichick decided to fix his safety problem in a notably creative way — by moving his best cornerback to the back line of his defense.

Cornerback is typically considered one of the most valuable spots in all of football. Go look at the contracts handed to corners and safeties. Minnesota safety Harrison Smith recently set the market at his position by signing an extension in June that included $28.6 million in guarantees. (Arizona’s Tyrann Mathieu wasn’t paid like a safety because when he’s right, he isn’t one.) Washington’s Josh Norman nearly doubled that ($50 million) with the contract he signed in April. In terms of money, draft status, and cachet, corners are held in significantly higher standing than their defensive back brethren, which makes it incredible that McCourty, in his move to safety, has somehow become more valuable to New England’s defense.

It starts with the unique athletic profile he brings to the position. Take a look at McCourty’s spider chart from the 2010 combine, brought to you by the wonderful Mockdraftable.com:

That’s not a bad set of scores! At 5-foot-11 and 193 pounds, McCourty was on the smaller side for any defensive back, but his 4.38-second 40-yard dash time and his overall movement skills did more than enough to compensate. Coupled with his college production, it made him worthy of first-round consideration. Now, let’s tweak the settings a bit and see how he compares to all the free safeties in Mockdraftable’s database:

The size figures obviously go down, but look at everything else. McCourty jumps from the 74th percentile to the 85th in the 20-yard shuttle, and from the 90th percentile to the 97th in the 40. Compared with corners, McCourty can move; compared to free safeties, he can move.

On film, it’s easy to see how that manifests itself. The Patriots have played a healthy amount of Cover 2 this season, keeping McCourty to one side of the field while either Duron Harmon or Patrick Chung patrols the other. When McCourty is assigned to a deep half, there’s no part of his territory he can’t cover. When he gets to play center field and roam the entire back end of the Pats defense, well, it can be a sight to behold.

This play, from the Pats’ 41–25 win over Buffalo in Week 8, eventually got called back because of a defensive holding penalty against cornerback Eric Rowe. But look at all the space McCourty traverses from his spot as the single-high safety. It’s nuts. He’s a weapon in large part because he brings a corner’s speed to a safety’s role, and it’s why he’s the best center-field safety this side of Earl Thomas when he’s actually asked to play there.

“[His transition is] pretty impressive because it’s a tough transition to make because you’re seeing the game from two different spots,” Belichick told reporters last month, after McCourty was named to his third Pro Bowl. “You’re seeing the game from outside-in on the perimeter and you’re seeing the game from inside-out with a lot of people that can get to you from the safety position.”

The ability to strangle an opponent’s deep passing game is one thing, but it isn’t the only reason that Belichick is quick to gush about McCourty. The seven-year veteran does a little bit of everything.

The play above is from the same Week 8 game against the Bills. This time, McCourty lines up as a cornerback against Buffalo tight end Charles Clay in the slot to the right side. McCourty nearly intercepts the pass as he sticks with Clay in coverage, and more importantly, moves like someone who came up playing the position. McCourty can still step in and be a corner when necessary, even though the Pats don’t do this a ton. (McCourty spends almost all of his time as one of two deep safeties.)

“We don’t use him in that situation a lot, but there’s times where it comes up and it’s certainly handy to be able to put him into those types of situations; extended tight ends, or extended backs, or things like that,” Belichick said earlier this week. “Or it could be an extended receiver in certain situations that you know that he can do that. … If you didn’t have that — you’d have to figure something else out.”

And that’s the key. McCourty’s flexibility makes him the answer to a variety of questions that inevitably come up throughout the season. When bouts of injury or ineffectiveness hit the Pats defense, Belichick knows he has a guy in his secondary who can play both corner and safety at an All-Pro level.

Going beyond identifiable skills, McCourty has earned the top compliment that Belichick and the Pats defensive staff could offer: He has their trust. Belichick has said that when McCourty comes off the field, the input he gives based on his vantage point has a ton of influence on the sort of tweaks New England will employ during the course of a game. McCourty is also responsible for most of the checks the Pats install in a given week. That’s a considerable burden to put on a safety, but there’s a reason Belichick talks about McCourty the way he does. The guy is Mr. Patriot.

If effusive praise isn’t enough (and it shouldn’t be), the Pats showed how much they value McCourty two years ago when he hit free agency. The night before signing with New England, McCourty reportedly called Belichick to thank him for five great years with the franchise. Unsurprisingly, McCourty had other suitors (the Eagles, Jaguars, and Titans chief among them) and had decided to jump on one of their offers. Belichick eventually called back to let McCourty know that New England had upped its bid. The team offered McCourty a five-year, $47.5 million deal that included $28.5 million in guarantees, the high for any safety at the time.

Typically, analyzing total value for NFL contracts is silly, because teams aren’t on the hook for money that isn’t completely guaranteed in later years. In McCourty’s case, though, it’s relevant. Barring injury or an unforeseen drop-off, he’s going to play out the length of that deal without blinking. It’s rare for teams to hand out a top-of-the-market contract and never think twice about it, but that’s exactly what happened in McCourty’s case. His ability to play all over New England’s defense and also act as its nerve center has made him as valuable as any safety in the NFL (again, non–Earl Thomas category). In a way, his flexibility has made his $9.5 million annual salary feel low relative to his overall impact.

“His judgment, his decision-making back there, which is a critical part of that position, is key,” Belichick told reporters in December. “But his coverage ability, his ability to play the run and the pass, play down, play back, play corner in some situations where we have to match a safety up outside on an extended receiver or tight end or something like that, things that he’s done a lot and comfortable with so he gives us a lot of versatility.”

If — excuse me, when — the Patriots knock off Houston on Saturday and head to their sixth straight conference championship game, we’ll hear all about the merciless march that Belichick and Brady have pieced together. It’s no coincidence, though, that those six years align with most of McCourty’s career. He’s the bedrock of the Patriots defense, no matter how infrequently his name comes up.