Fastest NFL rookie running backs were not combine's top speedsters

The rookie running backs who clocked the fastest times on the field last season with the ball in their hands were not the fastest backs at the 2017 combine. Six of the top 10 40-yard dash times came from running backs who didn't even crack this top 20 list of fastest on-field rookie backs. Sportradar tracked on-field speed last season, and here's a look at the 20 rookie running backs who topped the speed list:

Player MPH 40 time (combine)

Leonard Fournette (Jac.)22.054.51 (11th fastest)

Elijah McGuire (NYJ)21.174.53 (13th)

Alvin Kamara (N.O.)20.864.56 (16th)

Kareem Hunt (K.C.)20.844.62 (20th)

Dalvin Cook (Min.)20.454.49 (8th)

Trey Edmunds (N.O.)19.884.48* (Not invited to combine)

Tarik Cohen (Chi.)19.824.42 (3rd)

Matt Breida (S.F.) 19.804.37* (Not invited to combine)

Marlon Mack (Ind.)19.704.5 (10th)

Joe Mixon (Cin.)19.604.5* (Not invited to combine)

Chris Carson (Sea.)19.274.58 (17th)

James Conner (Pit.)19.194.65 (22nd)

Aaron Jones (G.B.)19.084.56 (15th)

Wayne Gallman (NYG)19.064.6 (19th)

Christian McCaffrey (Car.)19.044.48 (6th)

Corey Clement (Phi.)18.164.68 (Didn't run at combine)

Tion Green (Det.)18.06N/A (Not invited to combine)