METAIRIE, La. -- Identifying what has gone so epically wrong with the New Orleans Saints' defense is kind of like the age-old "chicken or the egg" debate.

The Saints keep changing their defensive players, coordinators and schemes because they’ve been so lousy on that side of the ball. But they keep struggling on defense because they have no continuity.

The Saints have started 55 different defensive players since the start of the 2014 season. And 23 different defensive backs have started at least two games in that 50-game span. Both are the highest totals in the NFL, according to ESPN Stats & Information.

By contrast, the Minnesota Vikings have used only 26 starters since the start of 2014. And the Denver Broncos have had only eight defensive backs start multiple games since then.

"There’s no consistency. I mean, there’s new faces every year. Nobody even gets to know each other. And because they’ve been bad, they just keep rotating guys," said former Saints linebacker Scott Shanle. Former Saints cornerback Jabari Greer echoed the same sentiment when asked for thoughts on why New Orleans has continued to struggle on defense through multiple players, coordinators and systems.

Dennis Allen, right, is the latest coordinator that coach Sean Payton, left, has turned to in an effort to fix a defense that has struggled to stop anyone over the past few seasons. Derick E. Hingle/USA TODAY Sports

In less than four years, the Saints have used five different players in the middle linebacker/"quarterback of the defense" role.

Some of it has been bad luck -- injuries to key starters such as Delvin Breaux, Nick Fairley, Keenan Lewis and Jairus Byrd, among others. Some of it has been impatience with players who were inconsistent in New Orleans but have thrived elsewhere -- such as Malcolm Jenkins and Akiem Hicks.

And a lot of it, Saints coach Sean Payton readily admitted Thursday, has been missing on too many defensive draft picks and free agents, including linebacker Stephone Anthony, a first-round selection in 2015 who was just traded to the Miami Dolphins for a fifth-rounder.

"They’ve just had issues with keeping a consistent starting 11 on the field," said Greer, who noted that was one of the strengths during the successful defensive seasons he was part of in 2009 (the Saints team that won the Super Bowl), 2011 and 2013. "And I think having a different voice in the leadership positions over the last three years is something that’s been a problem. They haven’t had a four-star captain like they do on offense with Drew [Brees] and Zach [Strief]. So when you have a shift in leadership that’s been dramatic over the past three years, you have the results.

"The roots are not as deep."

Burning through coordinators

To an extent, the defense has always been the Saints’ Achilles' heel during the Payton/Brees/general manager Mickey Loomis era. No NFL team has gained more yards since Payton and Brees first arrived in 2006 (405.1 per game). And no NFL team has allowed more yards (360.5 per game).

Some of those struggles date back to coordinators Gary Gibbs and Gregg Williams. But it has really become an epidemic since 2012 as the Saints have burned through coordinators Steve Spagnuolo (2012) and Rob Ryan (2013-15). Current D-coordinator Dennis Allen took the reins after Ryan was fired in November 2015. The Saints also fired longtime linebackers coach Joe Vitt and longtime defensive line coach Bill Johnson this year, bringing in Mike Nolan and Ryan Nielsen.

Under Spagnuolo in 2012, the Saints set the NFL record for most yards allowed in a season (7,042). Then, under Ryan and Allen in 2015, the defense set NFL records for most TD passes allowed (45) and highest opponents’ passer rating (116.1). This season, through two games, they’re on pace to shatter all three of those marks.

"I think having a different voice in the leadership positions over the last three years is something that's been a problem. They haven't had a four-star captain like they do on offense with Drew [Brees] and Zach [Strief]." former Saints cornerback Jabari Greer

Payton -- an offensive-minded head coach -- has been a constant through all the struggles. So it’s fair to wonder how much of a role he’s had in the defense’s demise. And he doesn’t shrink from that responsibility, saying, "It’s never gonna be the coordinator’s defense himself. It’s gonna be the Saints’ defense, No. 1."

Payton could be accused of running Williams out of town because of a personality clash, and of not having much patience with Ryan or Spagnuolo because of their historic struggles. But it’s hard to argue that any of those coaches deserved to stay, particularly considering Williams orchestrated the infamous bounty program that cost Payton a one-year suspension and the Saints two second-round draft picks.

Plus, Payton’s relationship with Allen is as strong as he’s had with any defensive coordinator, and that hasn’t proved to be a magic solution so far.

Ryan accused Payton and Loomis, in part, of ruining a good thing in 2014 by trying to mimic what the Seattle Seahawks were doing after the Saints had a good defense in 2013 (swapping out Jenkins for Byrd in free agency and drafting Stanley Jean-Baptiste in the second round in 2014, among other failed moves). But Payton ultimately fired Ryan during the 2015 season because his defense was too undisciplined and was plagued by assignment, alignment and substitution errors.

The area where Payton deserves -- and accepts -- the most blame is in the personnel decisions that have missed the mark the past several years.

The Saints whiffed on Anthony, Jean-Baptiste and several midround picks in the draft. And they whiffed on free agents such as Byrd, linebacker James Laurinaitis and cornerbacks Brandon Browner and Champ Bailey.

Payton and Loomis collaborate equally on personnel decisions, along with top personnel executives such as former personnel director Ryan Pace, current pro personnel director Terry Fontenot and current college scouting director Jeff Ireland. All have some hits and misses on their track record.

But Payton said they've been improving in recent years.

"From a personnel standpoint ... making sure that it’s something I’m comfortable with in regards to personnel and making sure that we’ve asked the right questions so we know the player can learn and we know the player can fit in this role [is important]. And I think that process recently has served us very well," Payton said.

Plagued by the secondary

Both Greer and Shanle note that the Saints bailed too early on Jenkins, who became a Pro Bowler with the Philadelphia Eagles (though in Hicks’ case, Greer said he understood why a change of scenery was probably a win-win).

"If Coach could go back, I’m sure that he would keep [Jenkins and safety Roman Harper in 2014], because they brought much more to the team than just performance and stats," said Greer, who now analyzes the NFL for TSN. "Their leadership and that stability on the back end was key to keeping our team mentally afloat when the hard times came.

Safety Kenny Vaccaro, a 2013 first-round pick, has been plagued by inconsistency as part of a secondary that has had tremendous turnover since the start of the 2014 season. Wesley Hitt/Getty Images

"We had a really good defense; we were pretty opportunistic. But the thing is, we were pretty consistent with the starting lineup. You know, we had the same 11 on the field for an extended period of time. ... Because in the middle of the game, when you’re in Week 8, 9, 10, you need to understand how your teammates play, what their tendencies are, how they react to motions, to shifts."

Greer pointed to an ugly play near the start of Sunday’s 36-20 loss to the New England Patriots: Second-year safety Vonn Bell moved rookie cornerback Marshon Lattimore out of press coverage after running back James White shifted from the outside to the inside, something Greer said is usually a no-no. And White wound up gaining 12 yards on the third-and-5 play.

"When I saw that, I realized that they were disjointed, that they were not communicating effectively. But those are little nuances you get when you’ve played with a player for a long period of time," Greer said. "Teams are gonna use motions and shifts to make those defensive backs communicate. And if they’re not comfortable communicating with each other, if they don’t know each other’s playing styles, they’re gonna be in for a very long season."

Saints safety Kenny Vaccaro is a 2013 first-round pick who has taken turns excelling and struggling throughout his four-plus-year career in New Orleans (including his benching late in the loss to New England). He has mentioned multiple times this year how difficult it is to develop chemistry with different players constantly rotating through the secondary.

"I’ve been here through it all, through a thousand different members in the secondary," Vaccaro quipped the other day.

Vaccaro was expected to be the one veteran member of the secondary to provide some glue and guidance this season, but he has struggled along with the younger players. Shanle said he and former Saints linebacker Jonathan Vilma have talked about how they would have loved to play with Vaccaro. But he said Vaccaro is "the most bipolar player I’ve ever seen as far as consistency. When he’s on, he’s one of the best players in the league. When he’s off, I just don’t get it."

Shanle said he sees potential in the Saints’ latest defensive incarnation, including rookie starters Lattimore, linebacker Alex Anzalone and safety Marcus Williams.

"But that’s been the problem -- they’ve been way too young on defense the past few years," said Shanle, who now analyzes the Saints for Cox Sports Television. "I believe that Dennis knows what he’s doing. But I don’t care if you bring Wade Phillips in, Buddy Ryan, whoever you want to bring in, I still think you’re not gonna have a great defense, just because some of the mistakes these guys are making on the back end.

"Everybody knows the secondary’s been the Achilles' heel of this team. I mean, we saw it in ’09 -- when we finally fixed the back end, we were able to do what we wanted to do on defense and be aggressive and play man [coverage]. Until you do that, all you do is try to do smoke and mirrors to cover up for those guys back there."