Pratt came to Oklahoma State as the No. 15 running back in the country according to Scouts Inc., and No. 139 on the 2009 ESPNU 150.
The team didn't release the reason for Pratt's exit, but it seems pretty simple. Perhaps personal reasons are involved, but my best guess is he doesn't want to play in new coordinator Dana Holgorsen's offense. The offense will get shifty backs like Kendall Hunter and Travis Miller the ball in space and allow them to make linebackers and defensive backs miss one-on-one in space.
Pratt is a 6-foot-1, 224-pound bruiser. Oklahoma State won't completely abandon running between the tackles, but it sounds like it's not going to be where running backs make most of their yardage. Add to that Pratt not even playing the traditional running back position, and it makes sense. Instead of fighting for time with Hunter, he's behind senior Bryant Ward (also just under 225 pounds) at a second running back spot.
Oklahoma State's depth chart this spring removed the tight end position in favor of a fourth receiver and removed the fullback position in favor of the second running back position where Pratt sits on the depth chart.
That's not a position change, per se, and I'm not entirely sure how the role of the second running back differs from the first, but it seems likely that Pratt didn't like it. At least he tried out Holgorsen's system.
Both sides should come out of this fine. Pratt didn't play last season, but he's clearly talented, and shouldn't have trouble finding a team who wants him. He didn't sign up to play in this offense, and no coach is going to blame him for transferring. Before signing with the Cowboys, Pratt had scholarship offers from Texas, Oklahoma, Texas A&M and Nebraska. The Navasota, Texas, native originally committed to LSU before reneging and heading to Stillwater.
Oklahoma State still has plenty of depth at running back. Hunter, a senior this season, is also backed up by redshirt freshman Jeremy Smith. Miller, a sophomore, was one of the spring's top performers for the Cowboys before sitting out most of the spring game after taking a big hit from safety Markelle Martin.