How “Little Dougie,” the skinny kid with Coke bottle glasses, blossomed into a big-play threat on the gridiron. And why, despite a limited role at Iowa State, he became a favorite of NFL scouts. Kene Nwangwu doesn’t look nervous, although he probably should. The former Iowa State running back is standing in the kick return huddle on an October evening in Ames, ready to put his heels on the five-yard line and take the lead role in football’s most violent play. His Cyclones need a spark—a strip sack left them trailing No. 17 Oklahoma by a touchdown with under nine minutes to play. “If you execute your job, I’m going to take this thing back,” he tells his teammates. When he catches the end-over-end kick, he isn’t thinking about the cascade of tacklers charging toward him or the cracking collisions around him. He’s transported home, away from the drizzling rain and biting wind at Jack Trice Stadium, to the Dallas heat rising off a rubber track and his teammate sprinting around its curv...