I’ve brought it up plenty of times here on numberFire, but the basic formula for evaluating a fantasy football player is Value=Opportunity x Talent. That is, the value of a player is determined by the amount of opportunity he sees on a football field and the sheer talent he possesses.

Opportunity for running backs comes in the form of attempts, while wide receivers see their opportunity in targets. The more opportunity, the higher chance that player has of being a top fantasy asset.

But, like I love to say, when you have high volume and high efficiency (a form of talent in quantitative form), you’ve got a fantasy football unicorn. Calvin Johnson? Unicorn. Adrian Peterson? Unicorn. C.J. Spiller in 2012? A fantasy football unicorn.

I certainly believe that opportunity is more important than talent in the fantasy football world, but high efficiency is vital for a player to produce in games where things may not be going said player's way. For instance, an early-down running back like Chris Ivory may appear, going into a week, that he’ll have a lot of opportunity, but if the Jets dig a hole early on in a game, he’s bound to see the field less. Therefore, in order to hold fantasy value that week, Ivory would have to do more with his low volume.

And that’s what this article is all about. Though some of these players were fantasy relevant throughout the year, most were handcuffed by opportunity. We may not be entirely sure how these players would have performed if they were given more chances, but my hope is to provide you with some analysis to show what might happen if they did (or do, in the future) see higher volume.

Toby Gerhart, RB, Minnesota Vikings

The Vikings backup runner ended the season with just 36 totes, but no running back with 30 or more carries was more effective on a per rush basis than Gerhart. He accumulated a Rushing Net Expected Points total of 9.61, giving him a 0.27 average. Moreover, his Success Rate, which measures the percentage of touches that contribute positively towards a player's NEP, was fourth-best in the league among the same runners, showing that Gerhart's efficiency didn't just come from a big run or two.

This season was sort of an anomaly for Gerhart though, who has been anything but efficient throughout his short career. In 2010, he saw 81 touches for a -0.10 Rushing NEP per rush, and in 2012 Gerhart’s Rushing NEP per rush was an abysmal -0.19, the third-worst in the NFL among rushers with 50 or more carries. His 2011 season did see a positive NEP per rush average, but it was barely over zero.

From a fantasy perspective, Gerhart could find himself on a new team next year with more opportunity, as he’s a 2014 free agent. I’m afraid his pretend pigskin value, however, will be dictated more on volume than raw talent, as the majority of his playing time has seen subpar results.

Ahmad Bradshaw, RB, Indianapolis Colts

People may have forgotten, but during the early parts of the 2013 season, Ahmad Bradshaw was the top back for the Indianapolis Colts. That is, until he suffered his inevitable injury, this one to the neck, ending his season.

But during his time, Bradshaw had 41 rushes for a Rushing NEP per rush average of 0.12, fifth-best in the entire NFL. It was only three games worth of running, so this isn’t to say that he’d keep up the LeSean McCoy-like pace, but again, it shows us that Bradshaw, with more opportunity (not getting hurt), could have been a surprising top fantasy back this season.

This really shouldn’t surprise anyone who’s followed Bradshaw over the course of his career though. He’s had 160 or more carries in four seasons prior to this one, averaging a Rushing NEP per Rush over zero in three of those seasons. That’s incredibly impressive, as the majority of running backs aren’t able to achieve positive values in the Rushing NEP department since it’s difficult to be efficient on the ground in today’s NFL. For some perspective, of the 31 160-plus attempt backs this season, just 11 of them had positive per rush NEP totals.

It’s not necessarily a question of “if” Ahmad Bradshaw is capable of being a top fantasy back. He’s done it before, and he’s consistently been efficient in the talent department. The problem is his health. Even if he gets another chance somewhere, trusting his durability is going to be difficult for fantasy owners to do.

Chris Ogbonnaya, RB, Cleveland Browns

Just when we thought Chris Ogbonnaya was going to break out, Edwin Baker stepped in and ruined the days of hundreds of fantasy owners.

Yet, it’s Chris Ogbonnaya who was consistently Cleveland’s most-efficient running back this year, finishing the season with a Rushing NEP per rush of 0.11, sixth-best among 30-plus attempt runners in the NFL. For some comparison, Edwin Baker finished with a 0.00 Rushing NEP per rush, while Willis McGahee was losing 0.16 points for the Browns each times he touched the ball.

Would Silent G be able to keep this up with more volume? It’s doubtful, as he saw 10 of his 39 touches on third down, a time where defenses are a little more worried about the pass than usual. That, and he’s been noted to not having the necessary skill sets to be a legitimate NFL running back. Even if the numbers see him having potential with more volume, the opportunity will probably never come.

All things remaining the same, Ogbonnaya will have flex PPR appeal in deep leagues again next year, but don’t count on him being “the man” anytime soon, especially when he had the chance this season and didn’t seize the opportunity.

Kenny Stills, WR, New Orleans Saints

Receiver’s a little more difficult to analyze in an article like this one, as high efficiency will usually favor wideouts who can catch the deep ball. We typically use the Reception NEP per target metric to note efficiency, which looks at the Net Expected Points added on each reception, divided by the number of targets that player gets. Clearly, one big play can make that type of ratio skyrocket, so filtering to have at least a decent floor targets-wise can help ease that a bit.

And that’s what I did. Looking at receivers with at least 50 targets on the season, no one had a better Reception NEP per target than Stills. Deep balls helped, sure, but even when you look at Target Net Expected Points only – the number of points a receiver adds for his team on all targets – Stills “still” ranked 18th out of the 106 30-plus reception receivers in the league this year within the category.

Stills is capable of getting open on crossing routes, and has been one of the more under-the-radar offensive rookies in the NFL this year. The best is yet to come, as long as he can continue to progress with Drew Brees.

Marvin Jones, WR, Cincinnati Bengals

The Bengals’ receiver saw more volume than Stills did, but still (man, I hate that his last name is Stills) ranked 55th at wide receiver in targets, seeing fewer than players like Chris Givens and Marlon Brown. Despite this, Jones finished the season with the second-highest Reception NEP per target, only behind the aforementioned Stills.

We all remember his four-touchdown game earlier this season, and although Net Expected Points weighs game situation over touchdown scoring, getting into the end zone certainly helps. His 10 touchdowns catapulted him towards the top of the efficiency list at receiver this season.

Jones was inconsistent from game to game this year, but that could just be because offensive coordinator Jay Gruden often times features different number two receivers opposite stud A.J. Green each game. If he – Gruden – is gone next season, perhaps Jones steps up and firmly plants himself as the number two target for Andy Dalton.

Jeff Cumberland, TE, New York Jets

This isn’t exactly someone I thought I’d write about in this column, but when sorting through tight ends, Jeff Cumberland’s metrics stood out. Of all tight ends with at least 30 targets this season, Cumberland had the best Reception NEP per target. And on all targets – Target NEP – Cumberland finished with a higher score than, wait for it, Rob Gronkwoski.

No, no – I’m not saying that Cumberland is even close to the kind of tight end Gronk is, nor am I even pretending that Cumberland will have any sort of role in fantasy football next year. But there’s no denying that, even though he was in a tight end committee most of the season, Cumberland was actually a very underrated player at the position in 2013.

He’ll be a free agent this offseason, so there’s a lot of ambiguity surrounding his role in 2014.