Wisconsin running back Melvin Gordon (25) runs out of the tackle attempt by Nebraska safety P.J. Smith (13) for a 56-yard touchdown run during the first half of the Big Ten championship NCAA college football game Saturday, Dec. 1, 2012, in Indianapolis.

In this Nov. 23, 2013, Georgia running back Todd Gurley (3) dives into the end zone for a touchdown.

Nebraska running back Ameer Abdullah breaks away from Southern California defenders on a 20-yard touchdown run during the second half of the Holiday Bowl NCAA college football game Saturday, Dec. 27, 2014, in San Diego. Southern California won 45-42.

Boise State running back Jay Ajayi dives for the touchdown as Arizona cornerback Jarvis McCall Jr. defends during the first half of the Fiesta Bowl NCAA college football game, Wednesday, Dec. 31, 2014, in Glendale, Ariz.

Miami running back Duke Johnson (8) is stopped for a loss by Florida State linebacker Telvin Smith (22) during the first half of an NCAA college football game, Saturday, Oct. 20, 2012, in Miami.

Indiana's Tevin Coleman, right, runs for a touchdown as Minnesota's Marcus Jones (15) watches during the second half of NCAA college football game in Bloomington, Ind., Saturday, Nov. 2, 2013. Minnesota won 42-39.

Alabama running back T.J. Yeldon (4) dives into the end zone for a touchdown as West Virginia's Travis Bell (26) and Karl Joseph (8) defend in the first half of an NCAA college football game Saturday, Aug. 30, 2014, in Atlanta.

South Carolina running back Mike Davis (28) escapes the grasp of Tennessee defensive back Justin Coleman (27) in the second quarter of an NCAA college football game on Saturday, Oct. 19, 2013 in Knoxville, Tenn.

Minnesota running back David Cobb (27) dives into the end zone for a touchdown against Middle Tennessee during the first half of an NCAA college football game on Saturday, Sept. 6, 2014, in Minneapolis.

Northern Iowa running back David Johnson runs the 40-yard dash at the NFL football scouting combine in Indianapolis, Saturday, Feb. 21, 2015.