Unlike one-on-one sports such as baseball or even ones based on even playing fields, such as golf, football is very much contingent on a variety of factors.

With 10 other players on the same side of the ball and another 11 on the other side, individual performances have nearly countless variables baked in.

That's why looking at running backs who outperformed their teammates in 2015 -- so, we're looking at players behind similar offensive lines and against similar opponents during the season, even though personnel constantly changes from play-to-play -- was an interesting exercise.

But what about the flip side? Which rushers couldn't stack up to their teammates?

The Process

At numberFire, we have a metric called Net Expected Points (NEP), which indicates how a team or player performs in terms of adding expected points on a given play. You can read more about it in our glossary.

The league-average Rushing NEP per play in 2015 was actually -0.04, so rushing is a bad way to gain expected points. Last year, only 14 teams' collections of running backs were better than -0.04, seven were above 0.00, and six were -0.10 or worse. Throwing in some team-by-team context probably can't hurt.

Comparing individual players to their teammates' combined Rushing NEP, Rushing NEP per play scores, and Rushing Success Rates -- the percentage of carries that lead to NEP gains -- can show us which guys fared well despite poor rushing situations and which guys underperformed in otherwise efficient rushing offenses.

We have to keep in mind that some teams have weak backup running backs, but what do the numbers actually show?

The Results

Last year, 14 backs with at least 100 carries (of 44 total) performed at least -0.02 Rushing NEP per play worse than their teammates' average.

It's really no surprise to see Chris Johnson on the list, as David Johnson was a standout last year, topping the position in Rushing NEP per play (0.15). LeSean McCoy's inclusion has a lot to do with how efficient Karlos Williams was (0.27 Rushing NEP per carry on 93 totes) as well as his personal mark of -0.01, which was still above the running back average of -0.04.

Matt Jones' -0.19 mark, worst among 44 backs with at least 100 carries last year, was bad enough that even Alfred Morris' -0.08 over 202 carries made it one of the worst team-adjusted results of 2015.

Similarly, Melvin Gordon's -0.19 and Latavius Murray's -0.07 still look bad when you consider what other backs on their respective teams pulled off.

Like we saw with the backs who outclassed their teammates, some older, more established names make this list as well. Marshawn Lynch, now retired, didn't stack up to his younger Seahawks teammates, and the same was true for Adrian Peterson.

The issue here is that players such as Peterson and McCoy offered nearly unmatched volume, and volume is often the bane to efficiency. So, what happens if we examine these difference in terms of Rushing Success Rate to see who excelled at adding NEP consistently relative to teammates. For context, the league-average rate for running backs was roughly 39% last season.

Only 10 players with at least 100 carries owned rates at least two percentage points worse than their teammates' collective mark.

DeMarco Murray makes the list again and looked terrible, relative to his teammates last season. Ryan Mathews' 46.30% and Darren Sproles' 45.87% Success Rates made Murray's 33.51% look even worse than it would have otherwise.

Chris Johnson, again, was dominated by David Johnson, but there's still some buzz that the elder Johnson will be a vital part of the Arizona offense, much to the chagrin of fantasy football owners.

Some rushers with significant volume -- Jonathan Stewart (242 carries, 39.26% Success Rate), Jeremy Langford (148, 43.42%), Mark Ingram (166, 39.16%) -- maintained league-average or better rates but were still a few steps behind their teammates. Latavius Murray (267, 34.46%) again looks bad relative to an already weak crop of rushers, but unless DeAndre Washington presses him for first-team reps, his volume could carry him to fantasy football relevance.

As for some backs with fewer than 100 carries, Andre Williams (88, 27.27%) was 18.46 percentage points behind the rest of the Giants' rushers, which includes Shane Vereen's 28.28% on 61 carries. That's how good Rashad Jennings's 50.77% on 195 carries was last year.

And in case you're piqued by Shaun Draughn in San Francisco, just know that his 32.05% on 78 carries was 4.68 percentage points worse than the rest of the 49ers' backs and that Carlos Hyde maintained a Success Rate of 42.61% over 115 carries, leading to a Rushing NEP per play of 0.02 compared to Draughn's -0.09.

Takeaways for 2016

Chris Johnson was bad in 2015, and that's multiplied by about a billion when comparing him to David Johnson's 2015 season. However, assuming that the talent wins out might not be a safe bet.

High-volume rushers such as LeSean McCoy, Latavius Murray, Adrian Peterson, and DeMarco Murray had significant efficiency issues not only due to volume but also relative to the rest of their teammates. Each enters 2016, ostensibly, as a starter, so it might not matter.

Matt Jones might not have what it takes to be a dominant rusher, but he's been impressive so far in the offseason.

Volume trumps efficiency when it comes to fantasy football, but some of these workhorse backs could fall victim to seeing reduced workloads to some more efficient backups.