Running back speed scores

2014 NFL Draft Running Back Speed ScoresAlthough it was created to help assist in the objective evaluation of NFL prospects, the only thing the combine usually creates is confusion. With a variety of drills that have murky relationships to actual game-day activities, fans and scouts in the corner of a particular player can point to any positive performance as a sign of success. What does it mean that a defensive end had the eighth-best short shuttle time? Who cares if a tight end benched 225 pounds 25 times? Without context, they are just numbers.So at Football Outsiders, we built in context. We've taken combine numbers and compared them to the future performance of those players to see whether they have any meaningful value in predicting success. No combine figure is ever going to be a foolproof indicator, but we have found that some drills are worth paying attention to at certain positions. And by making an adjustment to one drill -- the 40-yard dash -- for running backs, we came upon a metric that has a surprising level of relevance: Speed Score.The concept behind Speed Score is simple: Not all 40 times are created equal. When a 225-pound player runs a 4.48 40-yard dash, it's a lot more impressive than that same 40 time from player who weighs 185. On top of that, the range of 40 times for running backs is so small (from about 4.2 seconds to 4.9 seconds) that even a miniscule difference can be valuable. Times of 4.41 and 4.51 might look like roughly similar, but in the NFL holes can close up just that quickly. Adjust for those factors and you get the formula for Speed Score: (Weight * 200)/40 time^4. Multiplying the player's weight by 200 conveniently scales the metric so that an average Speed Score is right around 100. The average first-round pick approaches a Speed Score of 112. Since 1999, Speed Score has been able to explain about 20 percent of the variance between the DYAR and rushing yardage of NFL draft picks. In the past, Speed Score has pointed to the future success of mid-round picks like Brandon Jacobs (123.5), pushed speedy backs like Chris Johnson (121.9) to the top of their classes and suggested disappointing careers for future busts like William Green (98.7, a terrible score for a first-round pick) and Trung Canidate (99.3). Last year, Speed Score was sour on the likely rushing production of C.J. Spiller (107.5, below average for a first-rounder) and Dexter McCluster (a gruesome 75.0), but saw potential in sixth-round pick James Starks (106.3) and undrafted free agent LeGarrette Blount (105.8 ). On the other hand, Speed Score struggles with versatile backs who derive a significant amount of their pro value from their abilities as blockers and pass receivers, like Brian Westbrook (91.7) and Ray Rice (99.7). A player with a great Speed Score can also get sidetracked by injury, which felled top back Ben Tate (114.2) last year.So with all that said, did anything exciting happen at this year's combine?Antonio Andrews, Western Kentucky – 83.37 Dri Archer, Kent State – 105.06 George Atkinson, Notre Dame – 108.24 Kapri Bibbs, Colorado State – 89.15 Alfred Blue, LSU – 97.05 Ka’Deem Carey, Arizona – 84.84 Timothy Cornett, UNLV – 103.77 Isaiah Crowell, Alabama St. – 102.71 J.C. Copeland, LSU – 90.28 Timothy Flanders, Sam Houston St. – 81.33 Devonta Freeman, FSU – 93.96 David Fluellen, Toledo – 90.26 Tyler Gaffney, Stanford – 108.30 Marion Grice, Arizona State – DNP Jeremy Hill, LSU – 98.82 Ryan Hewitt, Stanford – 87.47 Carlos Hyde, Ohio State – 97.55 Storm Johnson, UCF – 93.36 Henry Josey, Missouri – 100.74 Tre Mason, Auburn – 100.96 Jerick McKinnon, Georgia Southern – 110.52 Adam Muema, San Diego State – DNP Ladarius Perkins, Mississippi St – 98.57 Silas Redd, USC – 86.89 Bishop Sankey, Washington – 102.85 Lache Seastrunk, Baylor – 97.17 Charles Sims, West Virginia – 106.25 Jerome Smith, Syracuse – 80.18 Lorenzo Taliaferro, Coastal Carolina – 104.09 De’Anthony Thomas, Oregon – 84.87 Terrance West, Towson – 105.92 James White, Wisconsin – 93.84 James Wilder, FSU – 83..17 Andre Williams, Boston College – 106.39 Damien Williams, Oklahoma – 113.22