This is the second piece in our four-part series about offensive position groups in the NFL. Part 1 is on quarterbacks. Part 3 is wide receivers. Part 4 is tight ends.

One great running back can carry an offense. A stable filled with them can transform one, though.

The NFL’s transition away from top-heavy backfields hasn’t come full circle yet, but the amount that can be devastated by a single injury continues to dwindle. Versatile running back rotations have become the norm rather than an exception, giving teams the opportunity to showcase a wide variety of ground options and a way to embarrass slow-footed linebackers through the air. A deep vein of multi-purpose backs can plaster over holes elsewhere in the offense and open up game-changing gaps for their offenses downfield.

So who does it best?

After ranking 2019’s backup quarterback situations, I decided to take on the running back (and, in a few cases, fullback) rotations that offer the most support to their clubs. The result was a lineup 1-32 of the NFL’s most potent backfields.

This array doesn’t only count star power at the top. The lineup is a look at depth and versatility at running back, so while stars like Todd Gurley, Saquon Barkley, and Christian McCaffrey may lead individual tailback listings, a relative lack of power behind them ultimately kept their groups from cracking the top five. The teams at the top of the rankings are the ones that can carve up a defense in a hundred different ways both on the ground and through the air — and the ones that won’t get derailed if their No. 1 back goes down.

Injuries and depth-sapping trades have already taken a toll on these rankings. The 49ers, once the deepest group in the league, dropped from the top spot into 10th, and even their place there depends on Matt Breida and Tevin Coleman being able to complement each other to drive an offense that badly needs playmakers. The Texans escaped from the bottom five only as long as Carlos Hyde can prove he’s not washed.

So, with an eye on depth, power, and flexibility in mind, let’s take a look at the strongest — and weakest — backfields in the league.

2019’s top five running back groups

Primary backs: Sony Michel, James White, Damien Harris, Rex Burkhead, James Develin

Tom Brady went from an understocked receiving corps to one of the league’s most loaded ones. But if injuries strike or he loses targets to suspension, he’ll still be alright. He’s got one of the league’s deepest backfields to bail him out.

Michel developed into a lead back and playoff hero as a rookie after scoring six touchdowns in three postseason games. White already owns the record for most receptions in a Super Bowl. Harris, a bit of a surprise pick in the third round, is a ready-made platoon back who averaged more than 6.4 yards per carry in college.

Rounding that group out is the dual-purpose versatility of Burkhead and the battering ram/space clearer/short route specialist Develin. Anything Harris, who was valuable in the preseason as both a runner and receiver, can add is just a nice bonus. No team in the league can throw more different looks at you out of the backfield than the Patriots.

Primary backs: Phillip Lindsay, Royce Freeman, Devontae Booker, Andy Janovich

Denver spent four draft picks on running backs between 2016 and 2018, only to have an undrafted rookie emerge as platoon leader last fall. Lindsay was a revelation in his first year as a pro, rushing for more than 1,000 yards on the season and 691 yards and eight touchdowns over his final nine games.

But he also ran out of gas as the season wore on and defenses adjusted, gaining only 100 total yards in his final three starts and suffering a wrist injury that needed months of recovery time through the offseason.

Fortunately, the guys who were actually drafted can pick up that slack, especially if Lindsay starts the season slowly. Freeman struggled through an up-and-down rookie campaign but remains a talented player who should grow in his second season as a pro. Booker is a useful pass catcher who excelled under a reduced workload last season (5.4 yards per carry).

The Broncos have plenty of questions to answer, but Denver has the horses to carry Joe Flacco and, eventually, Drew Lock.

Primary backs: Alvin Kamara, Latavius Murray, Dwayne Washington, ...Taysom Hill (kinda)

Kamara is still the player who butchered opponents through the air and on the ground in 2018. Murray proved in Week 1 he can be more than just the hammer New Orleans needs in short yardage situations. That duo’s ability to soften up defenses makes Drew Brees’ job all the more easier, and they’ll be counted on to step up should the veteran quarterback face another slump like he did to finish off last season.

Hill isn’t really a running back, but I bent the rules to include him since he gets the occasional chance to confuse defenses out of the backfield. Having a Swiss Army Knife like him gives offensive coordinator Pete Carmichael an entire new chapter in the Choose Your Own Adventure series the Saints write each week.

Primary backs: Tarik Cohen, Mike Davis, David Montgomery

The Bears’ rushing attack underwhelmed in 2018, but Chicago is hoping swapping out Jordan Howard for Davis and third-round pick Montgomery will recharge its backfield. There’s reason to believe it will work.

Cohen, the team’s major holdover from last year’s NFC North championship team, is a do-everything stalwart who is best deployed as a defense-glitching receiver but also contributes on the ground. Davis played a major role in Seattle’s refusal to tank in 2018, gaining more than 500 yards (on 4.6 yards per carry) and leading the Seahawks’ tailbacks in receptions (34). Montgomery was an elite space-creator in college whom Pro Football Focus loved, even if advanced stats did not.

David Montgomery forced 100 missed tackles rushing this season, almost double the next closest competitor in the Big 12. pic.twitter.com/AiSwrnqcHv — PFF College (@PFF_College) February 17, 2019

Primary backs: Ezekiel Elliott, Tony Pollard, Jordan Chunn

The return of Elliott and the emergence of Pollard as a slashing receiver from the backfield was enough to push Dallas into the top five. Zeke is a six-game suspension removed from leading the league in rushing in all three of his seasons as a pro. Pollard looked like a useful runner as the team’s primary option during Elliott’s preseason holdout, but his college career at Memphis shows he’s best used as a platoon option capable of sliding to the slot when needed.

2019’s bottom five running back groups

Primary backs: Kenyan Drake, Kalen Ballage, Mark Walton

Drake is fine, but his career so far has cast him as a part-time runner rather than the lead role he may face in 2019. Ballage averaged 5.3 yards per carry last season but is stuck in a similar situation. The good news is this group has the skills to overachieve. The bad news is Miami’s blatant tanking might prevent them from ever getting started.

Primary backs: Frank Gore, Devin Singletary, T.J. Yeldon

Betting against Gore is a fool’s errand, but he’s 36 years old and moving from a warm weather environment that helped revitalize his career (Miami) to one of the coldest home fields in the NFL.

Singletary was a touchdown machine at Florida Atlantic. Now he’ll have the chance to slide into a starting role if he can even be 80 percent as good against AFC East defenses. Yeldon was useful with the Jaguars, if unable to step into a starring role in northeastern Florida. This group could be more than the sum of its parts. Or it could fall apart entirely. The latter would be an extremely Bills thing to do.

Primary backs: Derrius Guice, Adrian Peterson, Chris Thompson

Guice continues to deal with injuries. Jay Gruden not only left Peterson off his Week 1 active list, but also roasted him while doing so. Thompson can be useful, though!

Primary backs: Leonard Fournette, Ryquell Armstead, Tyler Ervin, Devine Ozigbo

The Jags spent the No. 4-overall pick of 2017 on a player who has yet to average more than 3.9 yards per carry for a season. Fournette is a solid short-yardage back but, oh no:

Primary backs: Peyton Barber, Ronald Jones, Shaun Wilson, Andre Ellington

Bucs, your running backs. Woof.

Former second-round pick Jones will be better than he was in 2018 because he can’t get much worse. After being the 38th pick of last year’s draft, he ran for just 44 yards on 23 carries as a rookie.

Interested in the full team running back rankings? Here they are in all their glory, ready to be picked apart in the comments — RB1/2/3/4 designations come from team’s unofficial depth charts, culled during Week 2 of the 2019 NFL season.