6 Running Backs Who Drastically Outperformed Their Teammates in 2015

One of the more difficult aspects of evaluating players in the NFL is that the production of each and every player is dependent on the abilities of others. A wide receiver depends on his quarterback, a quarterback depends on his pass catchers, and a running back depends on his offensive line. How do you get a true idea of a player's talent if you can't separate him from the surrounding conditions?

Although it's far from perfect, one method is to compare that player to his teammates at the same position. For the most part, these guys will be dealing with the exact same conditions, making their relative performance a bit more indicative of talent. We did this with wide receivers earlier this week, but the same process can be conducted with running backs.

We'll be looking at these running backs through the lens of numberFire's Net Expected Points (NEP). This is the metric we use to track the efficiency of both teams and players, though we'll be focusing on the player side today.

To evaluate running backs, we'll be using Rushing NEP and Rushing Success Rate. Rushing NEP tracks the expected points added on each carry throughout the year. By using this as opposed to yards per attempt, a running back won't be penalized for picking up three yards on 3rd-and-2. Why should he get knocked if he got the job done and increased the team's expected points on the drive?

Rushing Success Rate looks at the percentage of carries on which the player increased the team's expected points for the drive. The average Success Rate among high-volume running backs this year was 39.91%..

After looking at each player who logged at least 30 carries this year, there were several who were able to separate themselves from their teammates. Here are six who did so, perhaps warranting additional carries in 2016.

David Johnson, Arizona Cardinals

Too obvious? Sorry. We'll get to some other names later, but we need to gush about David Johnson first.

Chris Johnson started the year off well enough, giving the Arizona Cardinals a steady hand they could turn to when necessary. However, his performance dwindled throughout the season, seeing his Success Rate dip all the way to 37.76 percent by the time of his injury. Then the younger Johnson went full ign'ant.

On the year, David Johnson turned 125 carries into 18.41 Rushing NEP or 0.15 Rushing NEP per carry. That went along with a 50.40% Success Rate, almost 13 percentage points better than the mark the elder Johnson posted. Whereas Chris Johnson was slightly below league average, David Johnson was one of the best rushers in the league, finishing second in Success Rate behind the next name on which we'll touch.

This means that Johnson's success is likely sustainable beyond 2015. The combination of a high Rushing NEP and a high Success Rate means that he's consistently getting his job done. If that offense can keep clicking the way it did this year, that could mean big things for Johnson in the fantasy realm next year.

Rashad Jennings, New York Giants

Rashad Jennings led the league in Success Rate. Andre Williams was last. We good here?

The New York Giants' backfield situation didn't have to be as gross this year as it was. Jennings turned his 195 carries into 4.44 Rushing NEP and 0.02 Rushing NEP per carry. Williams had -0.23 Rushing NEP per carry, meaning he was a full quarter point worse than Jennings on each attempt. But, yes, those 88 carries for Williams were completely necessary.

The Giants seemed to notice this over the final four games, where they started to pump the ball into Jennings' arms. There, he had at least 14 carries in each, resulting in 79 carries for 432 yards and 2 touchdowns. Good things happen when you feed efficient players, and Jennings showed exactly that.

It's hard to know whether this will be actionable information for fantasy football in 2016. Jennings is signed through 2017, but he's also entering his age-31 season. There isn't as much ware on the tires as other 31-year-old running backs, but it's still past the general tipping point of running back production.

If the team enters training camp with all else remaining the same, it would be a good idea to invest in Jennings if the price is right. We've seen that Williams can't be an effective NFL running back, and Jennings can. The age should bring Jennings with a reduced price tag, and that could be all he needs to return value.

Eddie Lacy, Green Bay Packers

Is this the ranting of a frustrated 2015 Eddie Lacy season-long owner? Let's just say Green Bay Packers head coach Mike McCarthy was an easy omission from my Christmas card list.

If we look at Success Rate, you may be surprised that Lacy generated frustration over the course of the season. He was ninth in the category of 44 running backs with at least 100 carries. James Starks was 40th.

Certainly part of the frustration with Lacy was his four fumbles during the regular season. This would be a fine critique if Starks hadn't put the ball on the turf five times himself. It makes Lacy's inconsistent usage -- at least in the rushing category -- a bit difficult to fully comprehend.

It should also be noted that Lacy's advantage didn't exist only in the Success Rate category. He finished the year with 187 carries for -10.31 Rushing NEP, while Starks was at 148 and -12.11, respectively. This put Lacy's Rushing NEP per carry at -0.06 with Starks' at -0.08. This is close enough, but the difference in Success Rate gives Lacy the clear upper hand.

The concern here is that neither player had particularly high numbers overall. That could depress Lacy's value moving forward if the Packers are simply not a good running team. However, with the number of injuries the team suffered on the offensive line this year, I'd hesitate before jumping to that conclusion. If recency bias drags Lacy's price down in the offseason, feel free to pounce and get him for a potential bounce-back season.

Karlos Williams, Buffalo Bills

Jennings' inclusion was largely because Andre Williams was utterly putrid. That's not the case with Karlos Williams and the Buffalo Bills. LeSean McCoy actually had a very respectable season, but Williams was still notably better.

With the sample size on Williams being only 93 carries, let's start this by looking at Success Rate. He finished the season at a commendable 49.46 percent. McCoy was still above the league average, but he fell well short of Williams at 40.89 percent. The gap is a bit wider when we look at the expected points.

Of the running backs with at least 80 carries, nobody was more efficient than Williams this year. He turned his 93 carries into 0.27 Rushing NEP per carry, the third best mark of any back with 80 carries in a season since numberFire started tracking NEP in 2000. McCoy was again solid at -0.01 Rushing NEP per carry, but it doesn't compare to what Williams did.

Unfortunately, this dominance doesn't really translate into much actionable information. Given what Buffalo gave up to acquire McCoy and the huge cap hit he carries in 2016, they're going to keep giving him the ball. Williams will be a huge contributor in games where McCoy is unavailable, but that's really all he'll be for the foreseeable future.

Spencer Ware, Kansas City Chiefs

Just to be clear, this is not harping on how much better Spencer Ware was than Jamaal Charles this year. Although Ware's numbers were better than Charles', Charles was still one of the best rushers in the league at the time of his injury. No complaints here. This is about who should back up Charles in the future, and the Kansas City Chiefs may have found their guy in Ware.

Because this is essentially a head-to-head comparison between Ware and Charcandrick West, let's put their numbers together. The table below shows how the two produced in their opportunities this year. Charles is also in there simply to provide greater context for the numbers.

We would be wrong not to throw out some dap to the Chiefs' offensive line for having three rushers with above-average Success Rates. Big dudes got it done. 

Although West was one of the backs who met that qualification with a quality Success Rate, Ware's dwarfed his. Ware's sample size isn't the largest, but the split between the two is at least fairly convincing.

The good thing for Ware is that West appears more similar to Charles in that he provides major value in the passing game. That could give Ware more of a role in the rushing game as the change-of-pace back once Charles returns.

At the same time, there's still not a ton of reason for optimism for Ware unless Charles gets dinged again. Charles played at least 74.3 percent of the team's snaps in each game he was healthy this year. If that number stays the same, Ware won't get on the field to make a difference. That said, he appears to be the one who should get first crack if Charles needs a breather going forward.

Bishop Sankey, Tennessee Titans

I would normally be hesitant to plug a guy with only 47 carries into here, as his success could merely be the result of a small sample size. However, the huge gap between Bishop Sankey and the rest of the Tennessee Titans' backfield makes this almost a necessary inclusion.

Four players on the Titans had at least 40 carries this season. I've included all of their rushing metrics in the table below so you can see the discrepancy for yourself.

At least after Sankey, the suckitude is pretty uniform. Almost freakishly so, in fact.

It's hard to figure out why the Titans decided to essentially put Sankey on shelf after the first few games. Given the lack of success out of Antonio Andrews in the middle portion of the season, it's surprising that Sankey found himself as a healthy inactive for several games. The coaching staff obviously had some reason, but it would seem to be something other than his performance when he did play.

As far as fantasy goes, you really can't trust Sankey at all unless coaches give you reason to think otherwise. If they seem to be indicating that he'll at least get a shot to nail down the job, then he might be worth a flier. The situation -- with the change in leadership and all -- is just too murky right now to inspire any confidence.