METAIRIE, La. -- Leonard Fournette is about to put one of the NFL’s most underrated streaks to the test.

The New Orleans Saints have not allowed a 100-yard rusher in 31 straight games, including the playoffs -- the longest active streak in the NFL, according to ESPN Stats and Information.

But now they will be facing a resurgent Fournette on his home turf at Jacksonville on Sunday. The powerful 6-foot, 228-pound running back ranks third in the NFL with 512 rushing yards after busting loose for 225 yards two weeks ago and 108 last week.

“He’s not just a load. Yeah, he’s a big guy, but he’s explosive,” Saints linebacker Demario Davis. “He has really good acceleration, really good in open space, good vision, can run routes out of the backfield.”

“He’s what makes that offense go,” defensive tackle Sheldon Rankins added. “A guy who can take it the distance from anywhere on the field. When you’ve got a guy like that who commands so much attention, you better bring your hard hat.”

That’s exactly what the Saints have done for nearly two full years now -- highlighted by their Week 4 win over the Dallas Cowboys, when they held running back Ezekiel Elliott to 35 yards on 18 carries.

Two things make the Saints’ streak even more impressive and unexpected.

For one thing, they have done it with a variety of players. Former starting defensive end Alex Okafor left in free agency, and they switched nose tackles from Tyeler Davison to Malcom Brown this offseason. Starting middle linebacker Alex Anzalone suffered a season-ending shoulder injury in Week 2 and was replaced by Kiko Alonso, whom the Saints acquired in a September trade. And Rankins missed the first three games of this season while recovering from the torn Achilles he suffered in January.

Secondly, this is a pretty seismic change for the Saints’ identity during the Sean Payton era (which has spanned a total of five defensive coordinators).

The Saints never finished in the top 10 in the NFL in run defense in Payton’s first 12 seasons before they finished second last year, allowing 80.2 rushing yards per game. They actually had the worst run defense in the league from 2012-15.

“I just think it’s a mentality, a mindset,” said Rankins, one of multiple players who credited third-year defensive line coach Ryan Nielsen -- a rising star in the coaching ranks who arrived from North Carolina State in 2017 -- for hammering home that stop-the-run-first philosophy.

Rankins and others also credited defensive coordinator Dennis Allen, who took over his current role midway through the 2015 season after Rob Ryan was fired.

“When you walk into each game -- especially now in this league -- you look at everybody’s backfield, they’ve got a guy who can pretty much take over a game,” Rankins said. “You know, we’re walking into a game this week against Jacksonville with Leonard Fournette, coming off -- what did he have, 225 yards or something like that?

“So it’s a mentality, it’s a mindset to try and neutralize that part of the game. And force teams to have to drop back and throw the ball and allow our rushers to go rush. I think (Nielsen) always preaches, ‘The way you get more sacks is to get more opportunities.’ If you’re stopping the run, then they gotta throw the ball more.”

Defensive end Cameron Jordan, who has emerged as one of the NFL’s elite pass-rushers with 28 sacks since the start of the 2017 season, has also embraced the mentality. Jordan was quick to point out that he was used primarily as a run defender early in his career as a first-round draft pick in 2011.

“I mean, clearly I take pride in my first and second down just to get to third down,” Jordan said. “That’s our emphasis. Some teams are emphasizing pass rush and getting up the field. We’re talking about gap integrity -- what it will take to hold a running back under 100 yards rushing or whatever it is.

“We’re trying to win every down, and that’s what it takes.”

The Saints’ personnel has a lot to do with it, too. Rankins, a first-round pick in 2016, and tackle David Onyemata, a fourth-round pick in 2016, both really started to break out with career-best seasons last year. And Davis was one of the better free-agent signings in the Payton era last year.

According to NFL Next Gen stats, Davis tied for second in the NFL last year with 16 “hustle stops” -- which are plays where the defender covered 20-plus yards of ground from snap to tackle. And Payton described the weakside linebacker as “one of those players that it's not a leaky two yards after he hits you.”

Veteran strongside linebacker A.J. Klein has been another solid free-agent addition since 2017. And while the Saints traded up in Round 1 for defensive end Marcus Davenport last year because of his prowess as an edge rusher, he is also holding his own against the run.

The Saints rank 16th against the run this year, allowing 108.4 yards per game. But they were missing both Rankins and Onyemata in Week 1. Since Week 2, they rank eighth at 90.5 rushing yards allowed per game.

“I think we're deeper in the defensive line than we were a year ago. And shoot, I think we're better across the board,” said Payton, who singled out the play of Brown and Onyemata so far this season. “I think Ryan and BY (Nielsen and assistant defensive line coach Brian Young) have done a great job, but I think that the depth has helped us.

“I think it's hard to find good defensive linemen. You have to draft them or pay a lot for ‘em. And we've been able to do that."