TEMPE, Ariz. — David Johnson’s first run in traffic was memorable, but not in a way that made his mother proud.

As a small child, Johnson, the Arizona Cardinals’ resplendent rookie running back, crossed a busy street with his sisters Danielle and Darnecia in Clinton, the Iowa town where they were raised. Upon finding out what they had done, Johnson’s mother delivered a tongue-lashing as severe as anything Johnson has absorbed from Cardinals Coach Bruce Arians.

In the second game of his N.F.L. career, Johnson ran into traffic and again emerged without a scratch, returning the opening kickoff against the Chicago Bears 108 yards for a touchdown. It was Johnson’s favorite rookie memory to date, mostly because his mother, Regina, was at Soldier Field to witness it. The smile on her face after the game made every trial and tribulation in Johnson’s youth melt away.

Johnson’s kickoff return, which matched the second-longest play in N.F.L. history, is a metaphor for his journey to the N.F.L. His path was longer than most, and it was hard to find any daylight early on. But Johnson seized the opportunities that others helped create for him to burst into national prominence.