Lingard had very good straight line speed. When he hit a good gap hole (A or B) in high school, he was going for big yards or a TD. But, from the first time I saw his film, I wondered about his upright running style (he's such an obvious track guy it's laughable). I hoped he'd be able to work on technique.
The second thing that stood out to me was his wiry build: the guy's clearly strong, and has little body fat, but his legs were not thickly built like an ideal running back. He would have to use the upper body to gain mass at the college level, rather than evenly distribute. Not ideal.
In the end, it didn't work, and it really shouldn't be very surprising.