Smith attended Paul Harding High School, where he received All-state and player of the year honors as a senior.

[3] As a redshirt freshman, he appeared in 10 games, opening the season against the University of Akron with 18 carries for 74 yards and one touchdown.

The next week against the University of Toledo he started to show a fumble problem, diminishing the coaching staff confidence in him.

On October 27, he was dismissed from the football team after a failed drug test and decided to declare for the NFL Draft.

On October 10, he was promoted to the active roster to provide depth while running backs Marshawn Lynch and Fred Jackson recovered from injuries.

On November 3, after injuries to Morris Claiborne and Barry Church, the Cowboys were forced to release him to make room for cornerback Leon McFadden.

[17] When Elliott was suspended for six games for violating the league's personal conduct policy, Smith ended up earning more playing time behind Alfred Morris.

[20] In Week 15 against the Oakland Raiders, Smith rushed for 13 yards and a touchdown as the Cowboys narrowly won by a score of 20–17.

[21] When Elliott returned from his suspension in Week 16 against the Seattle Seahawks, Smith's productivity dropped since he only rushed for 10 yards in that game.

[23] Smith wasn't a factor on offense as the backup running back, but maintained his role as a core special teams player.

His most action on offense came in the season finale against the New York Giants, registering 12 carries for 35 yards and one touchdown, when starter Ezekiel Elliott sat out to rest for the playoffs.

On December 10, 2019, Smith was signed by the Oakland Raiders, reuniting with special teams coordinator Rich Bisaccia, who served in the same role with the Cowboys.

[34] On September 8, 2020, Smith was signed to the New York Giants practice squad, reuniting with offensive coordinator Jason Garrett, who was his head coach with the Cowboys.

[35] On September 29, 2020, Smith was released from the Giants practice squad, to make room for another former Cowboys running back (Alfred Morris).

[42] Smith's younger brother, Jaylon, was a Pro Bowl linebacker in the NFL and a consensus All-American in college.