RTN: Why Lance Dunbar Is the Right Choice as the No. 2 RB

When the Cowboys drafted Oklahoma State running back Joseph Randle in the fifth round of the 2013 NFL Draft, they saw DeMarco Murray 2.0. There are some similarities between the two players, too. Both are tall, upright runners who found success in college as pass-catching backs. Randle hauled in 108 passes in his three seasons at Oklahoma State, a large number for a collegiate running back, and averaged 5.5 yards per carry (YPC) in a competitive conference.

The primary difference between Randle and Murray, however, is that Randle doesn't have outstanding straight-line speed. At just 198 pounds, he ran a 4.63 40-yard dash. Meanwhile, Murray checked in at 213 pounds and ran a 4.41, putting him in elite company.

We've had this talk before, and yes, there are slower running backs who have found success – some guy named Emmitt comes to mind. But when we use any stat, we're not looking for perfection. Rather, we want to tilt the odds in our favor. And using the 40 time as one of the tools to grade rookie running backs is a smart move. Since 2005, the most successful backs in the NFL in terms of approximate value have been the fastest, and it isn't even close.

When the Cowboys drafted Oklahoma State running back Joseph Randle in the fifth round of the 2013 NFL Draft, they saw DeMarco Murray 2.0. There are some similarities between the two players, too. Both are tall, upright runners who found success in college as pass-catching backs. Randle hauled in 108 passes in his three seasons at Oklahoma State, a large number for a collegiate running back, and averaged 5.5 yards per carry (YPC) in a competitive conference.

The primary difference between Randle and Murray, however, is that Randle doesn't have outstanding straight-line speed. At just 198 pounds, he ran a 4.63 40-yard dash. Meanwhile, Murray checked in at 213 pounds and ran a 4.41, putting him in elite company.

We've had this talk before, and yes, there are slower running backs who have found success – some guy named Emmitt comes to mind. But when we use any stat, we're not looking for perfection. Rather, we want to tilt the odds in our favor. And using the 40 time as one of the tools to grade rookie running backs is a smart move. Since 2005, the most successful backs in the NFL in terms of approximate value have been the fastest, and it isn't even close.

On average, a sub-4.40 running back has produced at over six times the rate as one in the 4.50-4.59 range. That's extraordinary. As much as everyone emphasizes quickness at the running back position, it's straight-line speed that matters most. There's a reason Jamaal Charles has the highest YPC in NFL history by nearly a half-yard.

When it comes to Randle, the deck seems to be stacked against him. He falls into a range of speed that few backs have been able to overcome. And the ones who have – Alfred Morris (so far) and Arian Foster – have a trait Randle doesn't possess: above-average size. Morris weighs in at 218 pounds and Foster is even bigger at 230. The faster you are, the lighter you can be, and vice versa. But being slow and lean isn't a good combination.

It's important that Randle was able to succeed in the Big 12. But when it comes down to it, the production for any running back is very dependent on his team. There's very little carryover for running backs in terms of college and NFL stats. Collegiate rushing touchdowns can explain only 0.7 percent of NFL touchdowns, i.e. you basically can't use a running back's college scoring to predict the same in the NFL at all.

Dunbar to the Rescue?

Let's start with the biggest concern: Dunbar weighs just 191 pounds. That's far from ideal, but it's less concerning than Randle's weight of 198 pounds. The reason is that Dunbar is just 5-8, actually a positive, while Randle is 6-0. There seems to be a positive correlation between not just weight and running backs success, but body mass index. Historically, the best backs have been stocky, i.e. short and thick. It's really one of the only positions at which shorter can be better.

Based on their heights, Dunbar trumps Randle in BMI: 29.0 to 26.9. If you look at the top 50 running backs in career rushing yards, only three had a BMI as low as Randle's: Tony Dorsett (ever hear of him?), Warrick Dunn and James Brooks. They were all faster than Randle.

Meanwhile, Dunbar checked in at 4.47 in the 40-yard dash as a rookie. That's still not elite given his small stature, but it's better than Randle. Using a metric called Speed Score, we can look at 40 times as a function of weight. A 4.60 40-yard dash from a 230-pound back – the numbers we saw from rookie Le'Veon Bell this year – is more acceptable than the same time for a 195-pounder. Below, I charted the Speed Scores for Dunbar, Randle, Murray and a few other notable running backs.

You can see that neither Dunbar nor Randle have elite speed scores (around 100 is average). Even if we account for weight and use Randle's superior Pro Day 40-yard dash time, he still checks in with the exact same speed score as Dunbar. Given the way Dunbar is playing in camp, the fact that he's (at worst) a comparable physical specimen to Randle means he should see the bulk of the No. 2 reps out of the gate.

Murray's Dominance

As a final note, look at how highly the Speed Score rates Murray. Due to his near-elite straight-line speed and excellent size, Murray checks in ahead of Jamaal Charles and just a bit south of Adrian Peterson. Since he's failed to remain healthy for a full season, we tend to forget that Murray has the potential to be a truly dominant running back. The numbers support the idea that Murray is primed for a breakout season.

But who will be his primary backup?

On average, a sub-4.40 running back has produced at over six times the rate as one in the 4.50-4.59 range. That's extraordinary. As much as everyone emphasizes quickness at the running back position, it's straight-line speed that matters most. There's a reason Jamaal Charles has the highest YPC in NFL history by nearly a half-yard.

When it comes to Randle, the deck seems to be stacked against him. He falls into a range of speed that few backs have been able to overcome. And the ones who have – Alfred Morris (so far) and Arian Foster – have a trait Randle doesn't possess: above-average size. Morris weighs in at 218 pounds and Foster is even bigger at 230. The faster you are, the lighter you can be, and vice versa. But being slow and lean isn't a good combination.

It's important that Randle was able to succeed in the Big 12. But when it comes down to it, the production for any running back is very dependent on his team. There's very little carryover for running backs in terms of college and NFL stats. Collegiate rushing touchdowns can explain only 0.7 percent of NFL touchdowns, i.e. you basically can't use a running back's college scoring to predict the same in the NFL at all.

Dunbar to the Rescue?

Let's start with the biggest concern: Dunbar weighs just 191 pounds. That's far from ideal, but it's less concerning than Randle's weight of 198 pounds. The reason is that Dunbar is just 5-8, actually a positive, while Randle is 6-0. There seems to be a positive correlation between not just weight and running backs success, but body mass index. Historically, the best backs have been stocky, i.e. short and thick. It's really one of the only positions at which shorter can be better.

Based on their heights, Dunbar trumps Randle in BMI: 29.0 to 26.9. If you look at the top 50 running backs in career rushing yards, only three had a BMI as low as Randle's: Tony Dorsett (ever hear of him?), Warrick Dunn and James Brooks. They were all faster than Randle.

Meanwhile, Dunbar checked in at 4.47 in the 40-yard dash as a rookie. That's still not elite given his small stature, but it's better than Randle. Using a metric called Speed Score, we can look at 40 times as a function of weight. A 4.60 40-yard dash from a 230-pound back – the numbers we saw from rookie Le'Veon Bell this year – is more acceptable than the same time for a 195-pounder. Below, I charted the Speed Scores for Dunbar, Randle, Murray and a few other notable running backs.

You can see that neither Dunbar nor Randle have elite speed scores (around 100 is average). Even if we account for weight and use Randle's superior Pro Day 40-yard dash time, he still checks in with the exact same speed score as Dunbar. Given the way Dunbar is playing in camp, the fact that he's (at worst) a comparable physical specimen to Randle means he should see the bulk of the No. 2 reps out of the gate.

Murray's Dominance

As a final note, look at how highly the Speed Score rates Murray. Due to his near-elite straight-line speed and excellent size, Murray checks in ahead of Jamaal Charles and just a bit south of Adrian Peterson. Since he's failed to remain healthy for a full season, we tend to forget that Murray has the potential to be a truly dominant running back. The numbers support the idea that Murray is primed for a breakout season.

But who will be his primary backup?