Running Back Growth Potential Starts with Size

He may never have been the consensus top choice in a fantasy draft, but Ezekiel Elliott is the perfect fantasy football player. His selection at fourth overall in the actual 2016 draft was a clear signal that he would start for the Cowboys immediately as a rookie. And since then, he has dominated the team's running back touches. He has never fallen short of 13 touches in a game and only five times fallen short of 18 touches. Since he has been healthy, Elliott has reached the rare benchmark of 300 PPR points in a season three times, tied for the most at his position in the last decade with Arian Foster and Le'Veon Bell. And Elliott would likely have gone four for four if he hadn't been suspended for six games to start his sophomore season.

I've been thinking about Elliott lately in relation to Christian McCaffrey, now the back with the best fantasy season of the last decade (470 points in 2019) and a player whose sophomore breakout in 2018 I did not see coming. It wasn't for lack of noise. In the preseason that year, beat reporters gushed that McCaffrey had put on muscle and was, as I read it, in the best shape of his life. That transformation was visible, but the latter cliché led me to underplay its importance. McCaffrey's 1.6 average yards after contact as a rookie was tied for fourth-lowest among the 47 backs with 100 or more carries in 2017. He had already been an important fantasy player, but more as a mislabeled slot receiver. I didn't expect the extra weight to turn him into Marshall Faulk.

McCaffrey enjoys his most obvious benefits from the extra weight on individual plays. He has increased his average yards after contact to 2.0 the last two seasons. But my reflection on Elliott and McCaffrey led me to conclude that weight has a greater importance for fantasy consideration in its impact on health. It is difficult to survive the workload needed to reach 300 fantasy points in a season. When you lay it out, the 20 backs who have reached that benchmark in the last decade look a lot alike.

McCaffrey's listed weight for this exercise is his combine weight. That is the source of all of my height and weight measurements, and so it comes up short when players transform their bodies after they reach the NFL. But even taking that handicap, McCaffrey is one of just four backs who hit the 300-point benchmark with a body mass index (BMI) below 29.0. Several others, such as Devonta Freeman and Aaron Jones, have similarly low weights to McCaffrey, but their shorter heights suggest a compactness to their builds. Those vagaries make BMI a better way to predict players' abilities to survive heavy workloads. Just look at the trends of the running backs who reached 240 fantasy points in season. More than half of them landed between a 29.0 and 31.0 BMI.

As Fantasy Points' Scott Barrett asserted on the latest episode of the Football Outsiders Fantasy Podcast, bell-cow running backs move the needle of full-season fantasy success more than any other type of player. Fantasy players recognize that value in established bell-cow backs such as Elliott and McCaffrey who should again be top-five draft picks in most fantasy leagues this year. But they have a harder time with younger players who haven't yet provided clear evidence of their peak professional workloads. For me, the BMI trends make it clear that backs who fall in that 29.0 to 31.0 range are the best selections for possible breakouts.

A.J. Dillon (33.0) is the only young back on the high side of the BMI range who rings my alarm bells. And even if they haven't thought of it in these terms, the critics of the Packers' 2020 draft strategy are applying a similar logic. Dillon looks like the sort of specialized short-yardage back that modern teams have stopped drafting on Days 1 and 2. Derrick Henry may have provided a reason to question that wisdom as he carried the Titans to playoff victories over the Patriots and Ravens, but Henry is a freak, and the athleticism of his 6-foot-3 and 247-pound frame pops in his 30.9 BMI. At about the same weight, Dillon is 2 or 3 inches shorter. I'll believe he can carry the Packers rushing offense when he does it.

Boston Scott (32.8) and Clyde Edwards-Helaire (31.8) don't alarm me as much as fill me with questions. I suspect most readers would have expected the 5-foot-6 Scott to show up on the other end of the spectrum, but his 203-pound weight is actually quite a bit for his height. Darren Sproles and Tarik Cohen are the only other modern, relevant backs who are similarly short, and Scott has more than 10 pounds on each of them. Without a reasonable player to compare him to, Scott has a wide range of possible career outcomes.

It's no mystery why Edwards-Helaire is a first-round fantasy pick this season. He is a decorated pass-catcher. He is a first-round selection of maybe the most fantasy-friendly offense, the Kansas City Chiefs. And after incumbent starter Damien Williams opted out of the season, Edwards-Helaire is left with little apparent competition for touches this season. But I've noticed that Edwards-Helaire is often described as a bowling ball, which for me conjures memories of another 5-foot-7 back, Maurice Jones-Drew, whom I remember as a standout yards-after-contact player. Based on his scouting, Edwards-Helaire isn't that. He relies instead on his vision, his quickness, and his hands. NFL backs can certainly succeed with those defining traits, but Edwards-Helaire tested slow with a 4.60-second combine 40 time and didn't try the shuttle or 3-cone drills that could have confirmed his quickness. I won't advise you to avoid him in your first rounds, but you should consider following his selection with either Darrel Williams or Darwin Thompson as a handcuff in the late rounds, assuming their pecking order is clarified before your draft date.

The lighter side of BMI offers many more reasons to be cautious in your sleeper picks. The Ravens have made it clear in their touch allocations and drafting of J.K. Dobbins (30.7) that Justice Hill (27.3) is a specialized pass-catcher. But Elliott's seemingly obvious handcuff, Tony Pollard (27.8), is no sturdier in view of his 2-inch height advantage. I'm unsure he could replace all of his lead back's heavy workload if he had that opportunity for a month or more. And I feel the same about possible Titans and Raiders rookie handcuffs Darrynton Evans (27.9) and Lynn Bowden (27.3). Austin Ekeler (28.0) and Raheem Mostert (28.3) have already enjoyed fantasy success, but I think it's fair to question their abilities to further increase their career-high 2019 workloads. That may cap both players as RB2s, even in PPR formats.

Meanwhile, many of the most compelling examples of players whose BMIs run counter to their assumed ceilings play in Elliott's NFC East and its AFC equivalent. After Edwards-Helaire, the Eagles' Miles Sanders (30.0) and the Bills' Devin Singletary (29.5) are KUBIAK's favorite backs that have never run at the volume we project for them this season. I believe they have the size and the skills to handle featured roles, even if the latter team's selection of Zack Moss suggests otherwise. Washington's Antonio Gibson (28.4) has a receiving track record to make even Edwards-Helaire jealous, but his 221-pound weight plays down at his height of 6-foot-1 to 6-foot-2. A finally healthy Bryce Love (30.3) might sneakily be a better upside pick. And while Sony Michel's return to practice may refute expectations that he could miss the start of the season, Damien Harris (30.0) has the build of a player who could handle that workload. He is a worthwhile lottery ticket whatever Michel's status to start the season.

As I've presented things so far, size is more of a subjective consideration to apply to the backs you could consider as sleeper picks with a reasonable assumption that KUBIAK or any other projection system cannot perfectly predict which starters will get hurt or lose their jobs. That said, proximity to "ideal" size is a factor KUBIAK uses to project workload changes for players in the same backfield over the course of a season. Take the Washington backs for example. Love's size advantage carries a smaller but still present advantage in our overall growth expectation -- which also factors in recent historical usage, efficiency, and prospect status -- over Gibson. We project the former player for a 1.3-carry weekly shortfall to start the season. But with their different growth rates, Love gains 5.1 more projected carries over the course of the season and nearly catches up to the Gibson's projected weekly total by Week 17.

We apply similar projected growths or declines to the backs and receivers on every team based on their potential and that of their teammates. And while that cannot simulate the repercussions the teams whose skill players suffer some major injuries this season will see, it does at least capture some of the value of player potential, even if that potential is unlikely to manifest as production at the start of the season.