The outfit Gregg Williams wears to every Jets practice fits him perfectly.

Not in the waist, inseam, shoulders and arms. Not a tailor’s fit. But figuratively.

Williams wears all black, and it suits him — because he is a villain to some people, an intimidating figure to others, a mystery to many and, the Jets would like to think, a hero to them as their defensive coordinator getting ready to face his most recent former team, the Browns, on Monday night.

(More on the Williams-Browns reunion in a minute.)

You’ll have a difficult time looking around the NFL to find a more polarizing figure — player or coach — than the enigmatic Williams.

“His reputation precedes him — he’s brash, he’s arrogant, he’s shocking, he’s all of those things,’’ former NFL linebacker London Fletcher, who played for Williams with the Bills and Redskins, told The Post. “But he’s also a great coach. He backs it up and he’s unapologetic about his approach and who he is.’’

Former Jets head coach Rex Ryan — whose father, Buddy, was a mentor of Williams in Houston — not surprisingly loves Williams’ bravado.

“He’s a passionate guy and he believes in himself,’’ Ryan said. “He’ll tell you how good he is. There’s a lot of people that can’t stand him, but he’s OK with that. That’s who he is. He thinks he’s the best. You’ve got to believe in yourself before anyone else will.

“He believes in himself and the guys respond to that. He’s confident, he’s got a little swag to him. Look, he’s seen a lot of huddles broken in his day and had a lot of success, and I think it was a great hire by the Jets.’’

Ryan and Fletcher are two of about a dozen players and coaches The Post spoke to who have either worked with Williams or know him.

Among those who declined to speak to The Post include Williams, who has refused to grant any one-on-one interviews since the Jets hired him, and anyone from the Saints, with whom Williams became most dubious for his kingpin role in the “Bountygate’’ scandal that got him suspended from the NFL for a year in 2012.

Messages left to more than a half-dozen Saints players who played for Williams during Bountygate went unanswered over the course of more than a week. Former Jets and Saints linebacker Jonathan Vilma, who was one of the reported ring leaders to the bounties, was one of those players who declined to be interviewed. After multiple attempts to reach Vilma through his employer, ESPN, Vilma finally said he was going to take a “pass.’’

This is an example of how polarizing Williams is. To some, like those Saints players who run and hide at the mere mention of his name, Williams is radioactive. To others, he’s the best, most caring, most knowledgeable coach they’ve ever played for.

There’s no in-between.

The worshippers

As difficult as it may be to find a more enigmatic figure in the NFL than Williams, it’s easy to find former players who are so loyal to him they will do (and did) anything for him. Many of them speak about how his coaching style molded them as players and helped change their lives.

Matt Bowen, who played safety for Williams in Washington, said Williams’ coaching style had such a profound effect on him, “I wanted to impress him every time I went on the field, even in practice.”

“That’s how highly I thought of him, that’s highly I still think of Gregg,’’ Bowen said. “Was it hard? Yeah. Where there days you felt like you could not make it through practice? Sure. It was very structured, very demanding, but [he’s] one of the best coaches I’ve ever been around in any level of the game.’’

Former Jets quarterback Neil O’Donnell played for the Titans when Williams was in Tennessee, and he said of practicing against the defense, “Gregg only made me better.’’

“With Gregg, you needed that rhino skin and not to worry about your feelings, because he was trying to make you the best possible player you could be,’’ O’Donnell said. “I think Gregg is going to make a huge difference in the Jets defense. He doesn’t accept losing, and I think that’s very important for that franchise now, somehow finding a way to get over that hump of the constant losing.’’

Local knowledge

Six coaches on the Jets staff either played or coached for Williams before.

“He basically kills a gnat with a sledgehammer,” said inside linebackers coach Frank Bush, who’s coached with Williams since their time with the Houston Oilers in the 1990s.

“Gregg’s a passionate coach who’s going to be himself,’’ receivers coach Shawn Jefferson said. “He’s fiery, he gets after it and his guys have taken on his attitude. Those guys have taken on his personality. I worked with Gregg in Tennessee. Great coach, but a better person.’’

Joe Vitt, the Jets’ outside linebackers coach and father-in-law of head coach Adam Gase, coached with Williams in New Orleans. He was implicated in Bountygate and actually testified against Williams in NFL hearings (the two later buried the hatchet). Vitt was terse when asked about him.

“If I didn’t love Gregg, I wouldn’t be back here working with him,” Vitt said.

“A lot of people have said things about Gregg in the past, but I love the guy,’’ Jets linebacker Jordan Jenkins said. “He’s intense. He’s loud. He’s an aggressive guy. He’s a take-no-[expletive] type of guy. He’s straight-up. If you respect Gregg, he respects you. Don’t listen to how he conveys the message. Listen to the message itself. He says what guys need to hear. He’s going to treat you like a man and you have to respond like a man.’’

In a training camp interview, Williams said, “I say what I mean and I mean what I say. You can’t BS players.’’

Three current Giants played for Williams. Jabrill Peppers was a safety for him in Cleveland. Janoris Jenkins was a cornerback for him with the Rams. And Alec Ogletree was a linebacker for him with the Rams. All three raved about Williams this week.

“Fiery, fiery guy,’’ Peppers said. “I think he can take guys places where they can’t take themselves. You have to have a certain level of discipline and mental toughness to play for him. You’ve got to listen to what he’s saying instead of how he’s saying it. If you’ve thin skin, you’re going to develop thick skin playing for G-Dub. It’s inevitable. Because he’s not going to change who he is.’’

Said Jenkins: “Gregg Williams’ whole motivation is to get you to play fast, and if you [expletive] up, we’ll correct that. Gregg is going to always be honest and up front with you. He’s not going to tell you what you want to hear, he’s going to tell you what you need to hear.’’

Ogletree said of Williams’ tough coaching style: “He did it out of love. He’s not attacking you as a person, he’s more so attacking the problem. He wants the best out of everyone. That’s what you want from your coordinator.’’

Monday night reunion

Williams, in his league-mandated media session with reporters Friday, will undoubtedly pass off Monday night’s game against the Browns, who did not retain him after his stint as interim coach last season, as “just another game on the schedule.’’

Bull. Not for him.

Williams, after taking over for fired head coach Hue Jackson, went 5-3 in his eight games. The last Cleveland head coach to post a winning record in his first season was Bud Carson in 1989. Then he was passed over for the permanent head-coaching position in favor of Freddie Kitchens.

If you don’t believe Williams is burning to beat the Browns on Monday night to show ownership what it missed out on, then you don’t believe there’s a large lake bordering the city of Cleveland.

“I don’t think you can possibly fathom how much he would like to show them the mistake they made,’’ said Kevin Gilbride, who was Williams’ offensive coordinator in Buffalo and is currently coaching the New York Guardians of the XFL. “I can tell you for sure that this will be a game he wants. Badly. Very badly.’’

Peppers is one of many who believe Williams was unfairly overlooked for the Browns head coaching.

“We won more games with him,’’ Peppers said. “I thought that was the name of the game.’’

Monday night?

“Oh yeah, he’s definitely going to be fired up,’’ Peppers said. “I can’t even fathom how he is in [Jets] those meeting rooms right now, because he’s the type of guy where if you tell him he can’t, he’s going to do everything he can to show you that he can.’’

Eddie Robinson, who played linebacker for Williams in Houston, Tennessee and Buffalo, on what his former coach will be thinking Monday night: “Maybe you should have rethought that one. If you don’t think I’m good, I’ll go out there and show you that I’m good.’’

Jeff Fisher, the former Titans and Rams head coach who employed Williams in both places as his defensive coordinator, said, “I thought Gregg was going to get more consideration as the Cleveland head coach, but I was told he was never considered.’’

Fisher insisted of the Browns game that Williams “is not going to let that be a distraction.’’

Dousing gasoline on the hot embers Thursday was former Giant and current Browns receiver Odell Beckham Jr., who claimed his Cleveland teammates told him Williams encourages his players to take cheap shots.

Beckham referred to a sprained ankle he suffered in a 2017 preseason against the Browns as a member of the Giants when he was undercut by defensive back Briean Boddy-Calhoun.

“I had players on this team telling me that’s what he was telling them to do — take me out of the game, and it [was] preseason,” Beckham said. “So you just know who he is. That’s the man who’s calling the plays [Williams].’’

Bountygate

Those Beckham words ripped the scab off an old wound, implications of Williams instructing his players to inflict harm on opposing players.

Williams, for whatever successes he’s had in the past and for whatever he accomplishes this season or in the future, always will be remembered for his role in Bountygate and the year-long suspension he received for his role in it.

In an audio of Williams addressing the Saints before a 2012 playoff game against the 49ers, he could be heard talking to his players about going for Frank Gore’s head, targeting receiver Michael Crabtree’s knee and tight end Vernon Davis’ ankles.

When NFL commissioner Roger Goodell came down on Williams, he paid the price while the Saints closed ranks, essentially leaving Williams on an island.

“It was tough on him, but he handled it and took his part in it,’’ Robinson said. “Unfortunately, he had to take the rap for it. He did and it probably set his career back a little. But it’s a testament to his will to say, ‘Hey, I’m not going to let that define me. I’m going to get back in there and keep working hard and earn the respect of the people who may not know me or prejudged me.’ ’’

Bowen, one of Williams’ most ardent supporters, penned a fascinating, behind-the-scenes, raw-truth article in the Chicago Tribune in 2012, detailing Williams doing the same thing in Washington a few years earlier.

It began:

“Prices were set on Saturday nights in the team hotel. In a makeshift meeting room, with the whisper of evening traffic pouring in from the Beltway, we laid our bounties on opposing players. We targeted big names, our sights set on taking them out of the game. Price tags started low during the regular season — a couple hundred bucks for going after the quarterback hard or taking a running back out below the knees. Chop him down and give a quick smile when you got back to the huddle. You just got a bonus.’’

Bowen revealed that he called Williams before he wrote the story and asked for his permission to write it.

“This is the situation I’m in and this is how I’m going to write the piece and I want your permission to do it,’’ Bowen asked Williams.

Williams gave Bowen his blessing.

“It was a motivational tool,’’ Bowen said of the bounties. “If you go back and look at the tape from that season, there weren’t dirty hits. They were clean hits. It was just a style of physical football and the [bounties] were just a motivational tool that we used as a team.’’

Bowen praised Williams for how he handled the aftermath.

“He accepted the discipline from the NFL, and has come back and to be the same coach he was in terms of his ability to teach and coach motivate players and look where he is now,’’ Bowen said. “He was just an interim head coach and now he’s the defensive coordinator in the biggest market in the league. And his players still love him. I think he did it the right way.’’

Robinson, one of Williams’ most trusted former-player confidants, praised his former coach because “he didn’t cry about’’ the penalty the NFL assessed him.

“He understood why it happened and how it got to that point,’’ Robinson said. “He just accepted it and said, ‘Hey, when I get my next chance I’m going to do better.’ ’’