He played college football at Notre Dame and was selected by the Detroit Lions in the sixth round of the 2013 NFL draft.

He rushed for 4,042 yards and 52 touchdowns during his high school football career, which also included a state championship in 2006, leading his team to victory and a perfect 12–0 season.

[4] As a freshman at Notre Dame in 2009 under head coach Charlie Weis, Riddick started off his career as a reserve and primarily on special teams as a kick returner.

[7] In 2010, under new head coach Brian Kelly, he made the move from running back to slot receiver.

[11] He also played running back following an injury to starter Jonas Gray near the end of the season.

[15] In the BCS National Championship, he had 37 rushing yards and a six-yard receiving touchdown in the 42–14 loss.

In Week 6, against the Minnesota Vikings, Riddick scored another touchdown on a nine-yard pass from Matthew Stafford as part of a 75-yard receiving game.

In the season opener against the San Diego Chargers, he had two receptions for 37 yards and a receiving touchdown.

[31] This set a Lions franchise record for running backs, surpassing the 662 receiving yards gained by James Jones in 1984.

[32] Riddick finished the season with 80 receptions and 697 yards, both franchise records for a running back.

[36] He was the Lions' top running back in 2016 after a season-ending injury to Ameer Abdullah in Week 2.

[38] He had been dealing with a lingering wrist injury towards the end of the season, leading him to be placed on injured reserve on December 31, 2016.