The League

PreDraft

Speed Score Clarifies RB 40 Times

In the cattle call that is the NFL Scouting Combine, the main event is the 40-yard dash. For all the other testing and poking and prodding that each player has to go through in Indianapolis, the 40-yard dash is the one event that every single athlete knows people will remember. Do you know who had the highest Wonderlic score in Combine history? What about the guy who had the best time in the three-cone drill? If you ask about the 40, though, people will start rolling off names like Darrell Green (reportedly possessor of a 4.09 40-yard dash), Deion Sanders (timed as fast as 4.19), and Bo Jackson (4.23). These are legendary athletes who became mythical figures because of their 40 time.

What hasn't been done before the last couple of years, though, is any analysis of whether the drills at the Combine mean anything. Do players with great broad jumps become excellent NFL receivers? Do quarterbacks need a big Wonderlic score to be smart enough to digest an NFL playbook?

For running backs, the answer is clear. A player's 40-yard dash time does bear a significant relationship with NFL success, measured by yards per carry, yards accrued, or DYAR, a Football Outsiders cumulative metric that adjusts performance for down, distance, situation, and opponent.

In playing around with 40-yard times, though, we noticed something; namely, not all running backs come in the same shape or size. It doesn't make sense to compare the 40-yard dash time of Trung Canidate (4.44) and LaDainian Tomlinson (4.46) and say that Canidate's likely to be a better back; Tomlinson outweighed Canidate by 28 pounds on draft day. His figure was far more impressive than Canidate's was, and it was confirmed by where the two were selected on draft day, as well as their careers thereafter.

Keeping this in mind, we've developed a metric called "Speed Score", which takes into account both a player's time in the 40-yard dash at the Combine as well as his weight. Speed Score bears a significant correlation to NFL carries (a correlation coefficient of .46 and a sign of a player's durability), yards (.46), and DYAR (.37), all at a level superior to that of strictly using the 40-yard dash time alone.

The metric is calculated by multiplying the player's weight by 200, and then dividing that figure by his 40 time, taken to the fourth power. Although it sounds like a bizarre calculation, the whole thing is pretty simple. 40 time is multiplied to the fourth power because of the huge difference there is in hundredths of a second for a player running the 40. The weight is multiplied by 200 to scale the metric so that an average Speed Score is just about 100. The average for first-round picks in the NFL Draft is 112.9.

Note, though, that this is true strictly of running backs and only with 40-yard dash times recorded at the NFL Combine. While other positions likely yield a strong correlation between speed score and NFL success, we're yet to test them and/or find metrics of NFL success that are satisfactory on a large scale. We throw out Pro Day data because of the dramatic differences in context from event-to-event with things like air quality, track quality, and even the type of shoes a player is allowed to wear.

We've calculated Speed Score for running backs going back through the 1999 season. The top ten performances that we've measured are a mix of mid-round steals, first-round picks, and a couple of players who never had careers.

Year Player School Picked Weight 40 Time Speed Score
2005 Brandon Jacobs Southern Illinois 110 267 4.56 123.5
2004 Kevin Jones Virginia Tech 30 227 4.38 123.4
2006 A.J. Harris Northern Illinois 231 4.40 123.3
2007 Jackie Battle Houston 235 4.42 123.1
2007 Chris Henry Arizona 50 230 4.40 122.7
2003 Justin Fargas USC 96 219 4.35 122.3
2008 Chris Johnson East Carolina 24 197 4.24 121.9
2005 Fred Staton Tusculum 249 4.50 121.4
2005 Ronnie Brown Auburn 2 233 4.43 121.0
2008 Darren McFadden Arkansas 4 211 4.33 120.0

The best Speed Score we've seen comes from Brandon Jacobs, who just beat out the injury-riddled Kevin Jones. Jacobs' rare mix of size and speed is precisely what's reflected in his Speed Score. The result is a player who is quick enough to go by linemen and heavier linebackers, but big enough to go through lighter linebackers and defensive backs.

Speed Score also finds successes in other body types, though. Although Chris Johnson's 197 pounds are below the average of an NFL halfback, the fact that he can run a 4.24 40 allows him to profile as a successful back at the pro level. If his 40 time was 4.38, a figure that would look good on someone like Jones, his figure would be a much less impressive 107.1.

Speed Score also does a good job of identifying players to avoid. Its lowest-scoring first-round picks are William Green (98.7), Canidate (99.3), and Chris Perry (102.7). In the second round, it would have argued against the selection of J.J. Johnson (92.3), Mike Cloud (92.5), and Kevin Faulk (94.0).

Faulk represents one of the flaws with Speed Score and an issue which may come up with one of the more prominent backs in the 2009 class. Faulk's had a successful NFL career for the Patriots as a versatile, change-of-pace back; Speed Score struggles to project those sorts of players as being successful because of their lack of straight-ahead speed. Another player who Speed Score doubted who ended up becoming a successful back was Eagles halfback Brian Westbrook (91.7), who represents the lowest score for any running back who enjoyed success at the NFL level.

Both Faulk and Westbrook are known for their all-around ability, a trait shared by the most prominent back in this year's class, Georgia halfback Knowshon Moreno. Moreno only registered a Speed Score of 96.9 at the Combine, which would give him the lowest Speed Score of any first-round pick in the last ten years were he to be selected among the first 32 picks. Because of his versatility, though, it's likely that Moreno will perform better than this athletic indicator might expect him to on the professional level.

His primary competition in the first round is Ohio State back Beanie Wells. Although Wells ran a 4.59 40 to Moreno's 4.60, the fact that Wells weighs 18 pounds more than Moreno yields a respectable score of 105.9, projecting him as a back likely to experience some success on the NFL level, although one more worthy of a second-round pick; by comparison, of all the backs chosen in the first two rounds of the 2007 NFL Draft, only Felix Jones (103.7) and Ray Rice (99.7) had worse Speed Scores than Wells, a fact which is reflected in scouts' opinions of the two sets of classes.

Looking for a sleeper? Try North Carolina State back Andre Brown. Although Brown was injury-prone in college, he's known as a versatile back who lacks the elite speed that the game's best running backs have. Speed Score might disagree.

Player School 40 Time Weight Speed Score
Andre Brown NC State 4.49 224 110.2
Cedric Peerman Virginia 4.45 216 110.2
Ian Johnson Boise State 4.46 212 107.2
Javarris Williams Tennessee State 4.52 223 106.9
Beanie Wells Ohio State 4.59 235 105.9
Kory Sheets Purdue 4.47 208 104.2
Donald Brown Connecticut 4.51 210 101.5
Rashad Jennings Liberty 4.64 231 99.7
Shonn Greene Iowa 4.63 227 98.8
Mike Goodson Texas A&M 4.54 208 97.9
Chris Ogbonnaya Texas 4.61 220 97.4
Marlon Lucky Nebraska 4.59 216 97.3
Knowshon Moreno Georgia 4.60 217 96.9
James Davis Clemson 4.61 218 96.5
Clen Coffee Alabama 4.58 209 95.0
Jeremiah Johnson Oregon 4.61 209 92.5
Bernard Scott Abilene Christian 4.56 200 92.5
Anthony Kimble Stanford 4.66 216 91.6
Javon Ringer Michigan State 4.60 205 91.6
Branden Ore West Liberty State 4.67 214 90.0
Tyrell Sutton Northwestern 4.66 211 89.5
Gartrell Johnson Colorado State 4.71 219 89.0
Kahlil Bell UCLA 4.68 212 88.4

By Bill Barnwell  |  April 6, 2009; 9:31 AM ET  | Category:  Combine , Draft Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   Del.icio.us   StumbleUpon   Technorati  
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Comments

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Mildly interesting. Of the top ten scores, A. J. Harris, Jackie Battle, Chris Henry, and Fred Staton were either busts or guys I've never heard of. While you report that the stats say speed score is a better predictor than 40 time, the correlations you report are with speed score as the only predictor. I'd be a lot more interested in the partial correlation with other predictors, like college YPC (for backs with over, say, 200 carries) and a measure of the level of college competition, in the model. I'm guessing a lot of the predictive power of speed score goes away when the correlations are adjusted for the effect of variables measuring prior performance. A combine stat is only interesting to me to the degree that it adds more information to what I already know.

Also, you're making the leap from saying that speed scores are moderately good predictors of performance (accounting for 15-25% of the variability) in all of the players included in your data to inferring that a high speed score might help you find a sleeper. I'd be interested in seeing how well speed sccre predicted NFL success in guys drafted in late rounds. I wouldn't be shocked if the correlations went negative, since true sleepers (guys who greatly outperform expectations for the round where they're taken) are likely to have dropped in the draft precisely because their measurables weren't good. So, maybe we want to look at guys whose speed scores underpredict their college performances if we want to find sleepers.

The best predictor of how well a person will do something new is how well he's done similar things in the past.

Posted by: Charles_Day@comcast.net | April 7, 2009 1:30 PM

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