Running backs with red flags heading into 2018
Mike Clay

It's no secret that volume is king in fantasy football, but a player needs to be #goodatfootball in order to earn and retain said volume.

Evaluating efficiency is far from an easy task in such a team-dependent sport overrun by variance and injuries, but over time, trends emerge. Analyzing categories like yards after contact (YAC), forced missed tackles and -- yes -- even yards per carry (YPC) can help us make the best evaluations.

The Jerick McKinnon problem

Though I'll be covering several players in this piece, the man who inspired it was McKinnon. After four seasons in Minnesota, the 2014 third-round pick and super-athlete heads to San Francisco, where he's positioned as the 49ers' feature back in coach Kyle Shanahan's running back-friendly scheme.

The hype surrounding McKinnon's 2018 prospects has been rampant and -- to some extent -- it adds up. Shanahan's running backs units have finished top-10 in fantasy points each of the past three seasons, and the likes of Steve Slaton, Alfred Morris, Devonta Freeman and Carlos Hyde had their best seasons in his offense over the past decade.

That's the good news.

The bad news is that McKinnon's efficiency has been downright awful during the past two seasons. Of the 38 running backs with at least 200 carries during the span, McKinnon ranks 37th in YPC (3.59) and 36th in YAC (1.51). Though he improved slightly in 2017, McKinnon came in below average in Pro Football Focus' "elusive" rating during the past two seasons of work. Last season's woes are especially concerning, considering he faced many light boxes (average of 6.5 yards per carry -- more on this topic later).

Though McKinnon has struggled as a rusher, he's been busy as a receiver, ranking top-15 at the position in receptions each of the past two seasons. Of course, his efficiency hasn't matched his volume. Among the 48 backs with 50-plus targets during the past two seasons, McKinnon ranks ninth in targets (121), 22nd in catch rate (78 percent), 34th in yards per reception (7.2) and 35th in yards per target (5.6). All that despite only 8.3 percent of balls thrown his way being "off target" (12th lowest).

McKinnon is an elite athlete, only 26 years old and sitting pretty as Shanahan's feature back, but a second-round average draft position (ADP) is quite pricey for a player who has never exceeded 159 carries in a season and has struggled badly with rushing and, to a lesser extent, receiving efficiency in recent years. Instead, McKinnon's likely backups -- Matt Breida and, in deeper leagues, Joe Williams -- are worthwhile late-round dart throws.

The rookie blues of Christian McCaffrey and Joe Mixon

Two years ago, I wrote an article about rookie-season efficiency, which concluded that even a relatively small sample of rookie touches could help us project a running back's future prospects. Perhaps more notably, research along the same lines showed that Jeremy Langford and Matt Jones were not long for the league. Last season, the study suggested we beware of Paul Perkins and Devontae Booker. So far, so good.

I dug further into the topic this offseason and the signs are still there -- backs who perform extremely poorly in YAC tend to struggle to carve out a successful NFL career. To show this, I pulled the 64 running backs who have handled 90-plus carries during their rookie season since 2009. The following charts show the top and bottom 12 in YAC.

Consider the careers of those 24 players and you'll be hard-pressed not to notice a trend. Of the 12 top producers, three were rookies last season (Kamara, Hunt, Mack), seven went on to fantasy relevance (Blount, Greene, Murray, Hill, Howard, Johnson, Ivory), one has been an injury-plagued bust (Rawls) and one had off-field issues (Williams). That's a pretty solid hit rate. On the other hand, a majority of the bottom 12 in rookie-season YAC have been busts and only two are positioned for significant 2018 roles. Crowell, who is expected to work in a committee with the Jets, is one of them.

The other -- McCaffrey -- stands out like a sore thumb, as he's been a consensus second-round pick in early 2018 fantasy drafts. McCaffrey was the eighth overall pick in last year's draft and went on to play 714 snaps as a rookie -- fifth most at the position. Of course, most of his damage came as a receiver; he ranked top-5 at the position in routes, targets, receptions, receiving yards, end zone targets and touchdown catches.

McCaffrey's receiving efficiency was solid, but the same can not be said about his rushing production. The Stanford product was limited to 3.72 YPC (1.41 YAC) in 117 attempts. That came despite McCaffrey seeing an average of 6.5 box defenders per rush, which placed him in the 23rd percentile. McCaffrey is expected to take on a larger chunk of the carries in his second season, but as research has shown, his early-career struggles should not be ignored. Fortunately for those looking to invest in him for fantasy, McCaffrey's massive role as a receiver will allow him plenty of fantasy production even if he flames out as a rusher. A "rich man's" Theo Riddick, if you will.

The other back worth a discussion is Mixon. Mixon was selected in the second round of last year's NFL draft and, at times, operated as Cincinnati's lead back as a rookie. Similar to McCaffrey, Mixon was much better as a receiver (88 percent catch rate, 9.6 YPR) and his rushing efficiency was shaky, at best. Mixon averaged 3.52 YPC (61st out of 72 backs with 50-plus carries), including a 1.72 YAC (44th). That post-contact production was underwhelming but doesn't quite put him on the spectrum of players we need to be concerned about.

However, if we turn to our friends at PFF, we see that Mixon ranked 49th out of 53 backs in elusive rating, having forced only 21 missed tackles on 208 touches. The fact that Mixon was dealing with injuries and Cincinnati's awful offensive line -- as well as his age (still 21) and prowess as a receiver -- creates plenty of reason for optimism, but his rookie-season play certainly raises some red flags. Those looking to hedge on Mixon should consider Giovani Bernard later in drafts, and deep-leaguers should take a look at 2014 fourth-round pick Mark Walton.

Rookie hype and Kalen Ballage

We're still in the early stages of charting and analyzing advanced college statistics with the goal of determining if and how well they can project a player's pro career. Two years ago, Jordan Howard was a player who stood out as a potential late-round star, and last season, Kareem Hunt and Chris Carson fit the bill. In 2018, the likes of Rashaad Penny (he was drafted higher than most expected, of course), Jordan Wilkins and Josh Adams are the names of note.

On the other side of the coin is Ballage. Miami's fourth-round pick has generated some serious hype since the draft (Matthew Berry and I may or may not have had some words on this topic at the FSTA conference in Minnesota earlier this month), with some expecting him to push or even overtake Kenyan Drake as Miami's lead back. The problem is Ballage was not an effective player at Arizona State. Yes, I know he once scored eight touchdowns in a single game. Yes, I know he's a freak athlete at 6-foot-1, 228 pounds with 4.46-second wheels in the 40. Yes, I know he crushed it at the Senior Bowl. But an athletic profile goes only so far. Ballage's efficiency was about as poor as you'll find.

After barely playing as a freshman in 2014, Ballage surged out of the gate the next season (5.22 YPC, 2.35 YAC on 125 carries). The wheels fell off from there. In 2016, he rushed for 14 touchdowns on 126 carries but was limited to 4.25 YPC and an ugly 1.43 YAC. He was only slightly better last season, posting a 4.26 YPC and 1.57 YAC. All easily ranked among the weakest in this year's running back class.

"But he's a great receiver," they say. This was true in 2016, when Ballage caught all but six of his 50 targets, averaging 10.7 YPR. He was not nearly as impressive on 18 targets in 2015 (5.0 YPR) or 32 targets in 2017 (4.6 YPR). Last season's 4.6 YPR was easily the worst in the 2018 rookie class.

Pro Football Focus does a good job charting forced missed tackles, and Ballage has ranked out poorly in its elusive rating each of the past two seasons. In fact, he was dead last in this year's class in both forced missed tackle rate (one every 8.6 touches) and elusive rating (28.7).

This isn't my way of saying Ballage (who is only 22) can't turn it around and carve out a successful career, but he also wouldn't be the first big, fast and athletic prospect to struggle in the pros. There's obviously plenty of reason for concern, which, when evaluating the Miami backfield, is why betting instead on Drake -- who was more effective at Alabama and has been outstanding thus far in the pros -- is the better plan of attack.

Accounting for the box with Todd Gurley II and Leonard Fournette

During my days at PFF, I was lucky enough to be overwhelmed with game-charting data and did my best to process it and convert it into (usually boring) columns during the offseason. Several of those pieces discussed box defenders and their significant effect on YPC. Recently, Josh Hermsmeyer, who operates and is smarter than I am, has taken even larger steps in this exact research. Josh's work inspired me to go back to the well and share some box data and its impact on running production in recent seasons.

Last season, 41 percent of 12,229 league-wide running back carries came against a six-man box and the average YPC was 3.94. Backs averaged 4.24 YPC against a six-man box (37 percent) and 5.84 YPC against five or fewer box defenders (4 percent). Going the other direction, backs averaged 3.74 YPC against an eight-man box (15 percent) and 1.41 YPC against nine in-box defenders (3 percent). Needless to say, the number of defenders in the box has a massive effect on YPC.

The chart below shows the YPC and adjusted YPC for the top 10 in carries during the 2017 season, as well as the gap between the two and average box defenders faced. Playoff data is included in order to maximize the sample.

The names that quickly jump off the page are Fournette and Gurley. Fournette has generated some criticism for his ugly 3.79 YPC over a league-high 338 rookie-season carries. A deeper look, however, shows that Fournette faced an average box of 7.1 defenders (90th percentile), which drove his "expected" YPC down to 3.85. That suggests it's fairer to call him average than it is poor.

On the other end of the spectrum, we have Gurley, who averaged just over a full yard more per carry than Fournette. Gurley, however, benefited from the Rams' three-wide-receiver-heavy scheme and faced an average of only 6.4 box defenders. That meant a 4.27 expected YPC, which was highest among 42 backs who carried the ball at least 110 times. Gurley was still better than Fournette last season, but more like half a yard per carry better, rather than a full yard (yes, that's significant). A comparison of YAC between the two (Gurley 1.88, Fournette 1.65) further confirms that the two were closer in effectiveness than is indicated by raw YPC.

Among all backs with 70-plus carries last season, Alvin Kamara's +1.4 gap between his actual and expected YPC was best in the league. Aaron Jones (+1.4), Dion Lewis (+0.8), Morris (+0.8) and Dalvin Cook (+0.8) rounded out the top five. On the flip side, Doug Martin (-1.0), Riddick (-0.9), Ameer Abdullah (-0.9), Jamaal Williams (-0.6) and Mixon (-0.6) were worst.

Using the same parameters, Bernard's 4.39 expected YPC was highest in the league. Rounding out the top five were Riddick (4.34), Tarik Cohen (4.29), Gurley (4.27) and Williams (4.26). Mike Gillislee's 3.50 expected YPC was lowest in the league, and he was followed closely by Jonathan Stewart (3.81), Chris Ivory (3.83), Fournette (3.85) and Adrian Peterson (3.87).