FanPost

Does NFL Size Matter? A Running Back Analysis

Jake Roth-USA TODAY Sports

[Editor's note: Promoted from the FanPosts.] -- In the days since the 2017 NFL draft, I have heard and read so much about the Eagles and their inability or unwillingness to get a 'feature' back in the very deep RB draft. Instead, they traded up in the 4th round to select the diminutive Donnel Pumphrey from San Diego State. Despite the fact that they addressed more important positions of need early on in the draft, the number of highly-touted backs either passed or missed out on left some fans panicking about the prospects of this upcoming season.

Lately, all we seem to be talking about is who can be the 'bell cow' or the big back the Eagles need. But do the Eagles really need a back bigger than the ones they will likely have on their roster in 2017? Does any team need a big back? I decided to delve into some data from Pro Football Reference to help me find out. (If you live under a rock, they do the work of gods by compiling data and allow users to query and download this data for wastes of time like this fanpost!)

What does an NFL Running Back look like?

The view below shows distribution of running backs based on height, weight, or BMI ranges. Please note that the zero was removed from the axis for an easier to read graphic. The scale of these differences is magnified as a result, but the practicality of these differences could be topic of debate. Select from the drop down to change the attribute. You can also drag the slider on the starting year to limit results to more recent times.

The dashboard shows that there is certainly a sweet spot for size with running backs, with most falling between 5-10" - 6'1" and weighing between 200 and 220 lbs. This is right where Ryan Mathews, Wendell Smallwood, and undrafted free agent Corey Clement find themselves. But more to the point, it shows there is not a whole lot you can gather by these size differences. For instance, the numbers of the 5'8" rushers are better than the 5'9", but the 5'10"-6'1" sweet spot rushers look better on average than the 5'9"-ers. So is it just really bad to be 5'9"? Obviously not in this context. Note that there is hardly any difference here on average, but just nitpicking these numbers shows there isn't much of a story to tell other than the sheer number of RBs that fit into these groups.

Short Yardage Success

Okay, when we look at general success, we don't see much, but what about 3rd and 1? Who on the Eagles is going to be the guy that gets us the 3rd and 1s and the goal line carries? We need a big, bruising "bell cow" for that, right? Common sense tells us yes. But I remember years ago measuring the effectiveness of Brandon Jacobs, just about the biggest back in the history of the league, with his Giants teammates. Brandon Jacobs seemed to have poor numbers against the Eagles at least in short yardage, and his smaller backfield mates fared better, almost no matter if it was Tiki Barber or Ahmad Bradshaw. I wondered if the same would apply across the history of the NFL.

The dashboard below shows first down conversion rates on short yardage downs, against the yards per attempt in these situations. The top view is all running backs grouped by size, and the bottom view is the individual best performers, regardless of position. Hover for detail.

The dashboard above shows that if you want to convert a 3rd or 4th and 1, you really should just QB Sneak it or give it to the fullback. Almost all the top performers with at least 10 attempts in this situation are quarterbacks. Most of the rest are fullbacks. My conclusion is that it matters more where they start from in the backfield than the size of the back.

In fact, from the above we really can make no correlation. Not only is the difference in the top and bottom small in percentage of conversion, the size sets are all over the place.

Compared to What?

Darren Sproles pretty much makes the 5'6" set. He has no real peer as far as height and weight in the NFL. He's the antithesis of Brandon Jennings, and a much better player. However, I don't think that can say anything about running backs who are 5'6" or 6'4". There are just simply not enough of them to know.

That brings us to Donnel Pumphrey. He's another guy who is on an island as far as his height and weight go. De'Anthony Thomas and Tavon Austin are of similar build, which doesn't instill a lot of confidence in Pumphrey alone. But it should be noted that he was a much more productive runner in college than these guys for obvious reasons. I simply can't rule Pumphrey out because we don't know much about RBs of his stature because they simply don't make it to the NFL. That might be enough to rule guys who don't fit the typical build out, but my thought on that would be that if the high school or college game would have washed them out if they were simply too small or big. A lot of guys probably do get their position moved to DB or CB with that stature. But for those that remain, are any as productive in college as Pumphrey. Heck, there are few RBs of any size that were.

Use the view below to look at backs of comparable stature to the Eagles current RBs.


So I say to those that think the Eagles need a big, powerful back, "Relax." Not only do they have guys that fit well within the normal confines of an NFL RB, but it might not even matter for the other guys on the roster. There can be nothing said about durability, effectiveness, or workload from size differences and I think that tells the biggest story of all.

YWZxUSO.0.jpg

Eagles' 4th Round Pick Donnel Pumphrey