The 2015 running back class is seen as a talented group, but which backs were most efficient -- and best -- on the field in 2014?

Is the incoming 2015 running back class the best group to enter the draft in the past 10 years?

Questions like the one above are fairly common when discussing this year's running back class, and if itâ€™s not one of the best groups to declare in quite some time, itâ€™s certainly among the deepest from a talent perspective. Zero running backs have been taken in the first round in the past two NFL drafts, and this year's class -- front-loaded with talent like Georgiaâ€™s Todd Gurley and Wisconsinâ€™s Melvin Gordon -â€“ could certainly buck that trend, regardless of your opinion on running back replaceability at the NFL level.

As the draft slowly lurks closer, itâ€™s time to start looking into some advanced statistics regarding this year's running back class. Of course, statistical production isn't the final word in the evaluation of college prospects, but it's certainly important in the process. With that in mind, letâ€™s get to it.

A Stacked Class?

Before we get in to the numbers, letâ€™s clear through a couple of disclaimers. In the table below, you will notice 15 running backs and their statistical production splits.

"Opportunity rate" is Bill Connellyâ€™s statistic that highlights the percentage of running plays where the back gained at least five yards. The following columns look at the percentage of yardage the running back gained on their relative carries along with the percentage of attempts that went for touchdowns.

For example, 27.3% of Florida State's Karlos Williams' carries went for a first down, which was just slightly above average amongst this year's class.

The data is sorted in ascending order by first name, and the best score for each individual yardage gained split is in bold. All of the data below is solely based on 2014 production -- no other previous years are included.

Player School Att. Opp. Rate 1st % 10+ % 20+ % TD% Ameer Abdullah NEB 264 41.1% 25.8% 17.0% 6.8% 7.2% Cameron Artis-Payne AUB 303 41.9% 27.4% 14.9% 4.6% 4.3% David Cobb MINN 315 39.4% 26.7% 15.2% 2.9% 4.1% David Johnson UNI 287 N/A N/A N/A N/A 5.9% Duke Johnson U Mia. 242 44.2% 29.8% 20.7% 7.9% 4.1% Javorious Allen USC 276 39.1% 26.1% 15.9% 2.9% 4.0% Jay Ajayi BSU 347 36.3% 22.8% 13.5% 3.5% 8.1% Josh Robinson Miss. St. 190 44.7% 27.9% 20.0% 6.3% 5.8% Karlos Williams FSU 150 35.1% 27.3% 16.0% 4.0% 7.3% Matt Jones UF 166 36.7% 20.5% 13.3% 3.0% 3.6% Melvin Gordon WIS 343 44.6% 29.2% 17.5% 10.2% 8.5% Mike Davis SC 199 39.2% 26.1% 13.1% 3.0% 4.5% T.J. Yeldon ALA 194 45.9% 24.2% 14.9% 2.6% 5.7% Tevin Coleman IU 270 41.5% 23.7% 17.4% 7.0% 5.6% Todd Gurley UGA 123 45.5% 35.0% 26.0% 8.1% 7.3% Average Â 244.6 41.1% 26.6% 16.8% 5.2% 5.7%

Instead of going down the entire list of running backs, here are some key takeaways from the advanced numbers above.

Todd Gurley 6â€™1â€, 226 Pounds (Draft Age: 20) | Georgia

Although Todd Gurleyâ€™s 2014 sample is significantly smaller than the other backs in this year's class (123 attempts) thanks to a four-game suspension and a torn ACL that cut his season short, his numbers were insanely efficient. He finished above average in every yardage gained split, and his 35% of carries that went for 10 or more yards demolished the entire group, as the next closest finisher in that specific split was Duke Johnson at 29.8%.

Among draft circles, Gurley is conventionally the number-one overall running back in this year's class, but certainly has his red flags, most notably his ACL tear back in mid-November. Itâ€™s also possible that his incredible efficiency at Georgia in 2014 was just the result of a limited amount of carries. But itâ€™s worth noting that his 2014 numbers were on 20.5 attempts per game. Plus, his overall statistics weren't too far off of his career averages that went for a first down (29.4%), 10-plus yards (22.4%), and 20-plus yards (6.5%).

Melvin Gordon 6â€™1â€, 207 Pounds (Draft Age: 22) | Wisconsin

Almost equally to Gurley, Gordon showed very well in these advanced statistics, finishing above average in each split and leading all running backs in percentage of attempts that gained 20-plus yards. Gordon also finished with the highest percentage of attempts that went for a touchdown (8.5%). What makes Gordonâ€™s case so impressive is he was incredibly explosive on a high number of carries (343), and with a ton of attention from opposing defenses like this, where eight defenders are stacked in the box.

Duke Johnson 5â€™9â€, 206 Pounds (Draft Age: 21) | Miami

Miamiâ€™s Duke Johnson also popped up as a back with excellent production in his junior year of college. He finished fifth in opportunity rate, second in both first down and 10-plus yard carry percentage, and his 7.9% of attempts that went for 20-plus yards was good enough for third among the group. This is a good example of Johnson's explosiveness on display.

Conversely, Johnsonâ€™s combine results were ultimately a bit of a letdown, but his college production obviously tells a different story.

Ameer Abdullah 5â€™8â€, 198 Pounds (Draft Age: 21) | Nebraska

Unlike Duke Johnsonâ€™s 2014 production, Nebraskaâ€™s Ameer Abdullahâ€™s output wasnâ€™t necessarily sub-par, but he stayed near average through each statistical split. Thatâ€™s not to say Abdullah lacks an explosive â€œworkhorseâ€ mold though. Abdullah posted a 42.5 inch vertical leap at Februaryâ€™s combine, and tested very well overall, finishing in the 98th percentile in the 20-yard shuttle and the 93rd percentile in the 60-yard shuttle.

Tevin Coleman 5â€™11â€, 206 Pounds (Draft Age: 22) | Indiana

Tevin Coleman might be the most divisive back in this years class. Like Abdullah, his college production isnâ€™t necessarily bad, but it also leaves a little pause for concern. Adding to these question marks, Coleman didnâ€™t participate in this year's combine due to a toe/foot injury that caused him to have surgery in December last year. Coleman is a bit of a boom-or-bust runner, and his running style is very aggressive, where he sticks his foot in the ground and eats up yardage in a hurry.

This is a decent example of Coleman's one-cut ability, and for an example of his boom-or-bust long-speed on display, click here.

T.J. Yeldon 6'1", 226 Pounds (Draft Age: 21) | Alabama

Yeldon is a fairly interesting case study in this year's running back class. His 45.9% opportunity rate led all of the 15 running backs, and is ultimately a good sign, but he also came in below average in every other advanced statistical split. Sure, Alabama's strength of schedule was brutally hard last year, but the fact Yeldon was running behind some of the most highly-recruited offensive lineman in the country invariably equals the schedule aspect out.

It also doesn't help that his combine measurables weren't stellar -- RotoUnderworld's Player Profiler has Yeldon flagged with a 44th percentile athleticism score, which is a major downer. Yeldon still does possess great size, plus his young age certainly works in his favor. But, barring in mind production and athleticism isn't a sole determining factor of a running backs ability, his sub-par statistics shouldn't simply be ignored.

5'11", 229 Pounds (Draft Age: 21) | Minnesota

In a sort of roundabout way, Cobb is probably the most landing-spot dependent back in this year's class. Production-wise, he came in below average in four of five statistical splits, and only nine of Cobb's 315 carries in 2014 went for 20-plus yards, which indicates he may be a bit of a grinder. Though he may not show the ability to be a super explosive runner, he's pretty powerful at the point of contact, as shown in this run against Michigan.

Unfortunately, due to a quad injury that harpooned his 40-yard dash time, we don't have solid measurables to compare other running backs to Cobb. Though before his unfortunate leg injury, Cobb did a few drills, and one positive sign of his explosion is a vertical jump of 38.5 inches, which landed him in the 90th percentile of running backs.

6'0", 221 Pounds (Draft Age: 21) | Boise State

Ajayi's production suffers among the group, but it's worth mentioning he had a DeMarco Murray-level workload at Boise State in 2014, touching the ball 28.3 times per game. His massive workload shouldn't write off any statistical concerns, but it's fairly evident Ajayi's style of game isn't about long runs like Tevin Coleman's is. Also, as his 397 touches in 2014 would indicate, Ajayi possess three-down ability in an NFL offense, and his solid athletic profile is certainly a boon to his overall potential.