News & Analysis

Don't expect a fullback to help David Johnson (not that he needs it)

By Scott Spratt
Jun 6, 2018

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GLENDALE, AZ - DECEMBER 04: Running back David Johnson #31 of the Arizona Cardinals runs for a first down as Su'a Cravens #36 of the Washington Redskins attempts to make a tackle during the second quarter of a game at University of Phoenix Stadium on December 4, 2016 in Glendale, Arizona. The Cardinals defeated the Redskins 31-23. (Photo by Ralph Freso/Getty Images)

June marks the start of the “best shape of his life” summer months in football. Everyone has had a chance to reconcile their opinions from the draft and free agency, and so most of the stories left to come out of OTAs have a bit of a manufactured taste. Still, one or two inevitably pique my interest, and my junk food of choice so far this year is the Cardinals’ bringing in a fullback (Derrick Coleman) for David Johnson. Adam Stites of SB Nation and Josh Weinfuss of ESPN each reported on that development under new offensive coordinator Mike McCoy, who will replace the notoriously three-receiver-reliant and now-retired Bruce Arians as the team’s play-caller.

It’s easy to become caught up in the optimism of the quotes in those stories. After all, it makes sense that a fullback would improve a team’s running efficiency — likely at the expense of its passing efficiency — since the most obvious of his responsibilities is to serve as a lead blocker on running plays. But like so many strategies in football, fullbacks have a collateral impact that can be difficult to see when you focus exclusively on the path of the ball. And those ancillary effects seem to counterbalance whatever benefit a fullback provides by taking out the first defender to hit the hole.

It actually took a bit of work to realize even that value-neutral conclusion. With only a surface-level attempt at research, I found that running backs experience a marked decrease in their yards per carry from 4.2 yards without a fullback on the field to 3.8 yards with one. Those numbers are weighted for specific running back seasons, so they aren’t biased by any quality differences in the running backs that play for teams that rely on fullbacks and those that don’t. However, they are biased by context. It turns out that running plays with a fullback on the field have a lower expected yards-per-carry average than plays without a fullback, based on my Yards Added research. Put differently, teams tend to use fullbacks on plays where they would expect to gain fewer yards with a carry, such as near the goal line or on third or fourth down with just a few yards to gain for a new first down.

When I created my expected yardage model, I did not use the presence of a fullback as a model parameter. And so if fullbacks moved the needle in expected production for running backs, then there should be a split of positive yards added on all plays with fullbacks and negative yards added on all plays without fullbacks. Instead, running backs produce right at their expectations with and without a fullback.

RB Performance With and Without Fullbacks, 2009-17
Test Fullback No Fullback Diff
YPC 3.83 4.21 -0.38
YPC – ExpYPC 0.04 0.02 +0.02

I think the most likely explanation for the non-import of fullbacks is that their presence telegraphs a likely running play to the defense, which can then respond with personnel skewed to stop the run. Counterintuitively then, a fullback might do more to help a team’s passing attack than its running attack if its quarterback is particularly adept at play-action passes. But those are concerns for Sam Bradford and eventually Josh Rosen; Johnson doesn’t look likely to improve his efficiency when he carries the ball behind a fullback.

Johnson doesn’t seem overly likely to see his total of touches ratchet up because of a fullback, either. Year-to-year changes in a team’s percentage of carries with a fullback on the field do not correlate with changes to either their ratio of run-vs-pass or that ratio near the goal line. Many of the most radical regime changes had the opposite effect of that hypothesis. Kyle Shanahan’s 49ers and Jim Caldwell’s Lions rushed less often than their fullback-averse predecessors, Chip Kelly and Jim Schwartz. Arians himself relied more heavily on the run when he joined the Cardinals in 2013 than the man he replaced, Ken Whisenhunt, did the year before.

New Regimes with the Biggest Change in % of Plays with a Fullback, 2009-17
Team Seasons Coach1 Coach2 Fullback% Run Ratio
SF 2016-17 Chip Kelly Kyle Shanahan 46.5% -8.0%
DET 2013-14 Jim Schwartz Jim Caldwell 36.6% -1.5%
JAX 2016-17 Gus Bradley Doug Marrone 30.6% +11.4%
BUF 2009-10 Dick Jauron Chan Gailey 23.7% -5.6%
MIA 2011-12 Tony Sparano Joe Philbin 16.0% -3.6%
NYJ 2014-15 Rex Ryan Todd Bowles 15.6% -7.9%
CLV 2013-14 Rod Chudzinski Mike Pettine 15.2% +14.7%
MIN 2013-14 Leslie Frazier Mike Zimmer -21.7% +0.6%
JAX 2011-12 Jack Del Rio Mike Mularkey -22.4% -13.0%
NYG 2015-16 Tom Coughlin Ben McAdoo -23.8% +0.7%
ARZ 2012-13 Ken Whisenhunt Bruce Arians -24.6% +5.9%
SD 2012-13 Norv Turner Mike McCoy -26.6% +3.5%
OAK 2014-15 Dennis Allen Jack Del Rio -27.3% +3.0%
SF 2015-16 Jim Tomsula Chip Kelly -38.7% +5.7%

None of this is exactly bad news for Johnson’s fantasy prospects this season, but hopefully it will temper your perception of his value if this buzz builds momentum for him in drafts. The running back fantasy landscape has changed dramatically since Johnson and Le’Veon Bell were the consensus top two picks this time last year. Todd Gurley had his renaissance. Ezekiel Elliott cleared his suspension. Alvin Kamara, Kareem Hunt, Leonard Fournette, Dalvin Cook, Christian McCaffrey, and Joe Mixon basically doubled the number of backs with three-down potential, and Saquon Barkley is as close to a lock as there can be to join their ranks this season. You can make a reasonable case that Johnson belongs ahead of most of those backs, but he definitely isn’t a tier above the bulk of them the way he was last year, fullback or not.

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