Lions head coach Matt Patricia announced the moves Saturday morning:
Detroit selected Riddick in the sixth round of the 2013 NFL draft out of Notre Dame.
The 28-year-old New Jersey native typically filled a third-down role for the Lions. His number of receptions (285) nearly matched his amount of carries (288) across six years with the team. He's recorded at least 50 catches in four consecutive seasons.
Detroit signed veteran running back C.J. Anderson during the offseason. It created a logjam in the backfield as he joined Riddick, Kerryon Johnson and Zach Zenner in the battle for snaps.
"The talent level has risen, so I mean yeah, we're going to compete," Riddick told reporters Friday. "The competition is already there, again, we just have to show and bring our A-game."
Riddick, who's coming off his least-productive year since his rookie season with 555 yards from scrimmage and no touchdowns, quickly became the odd man out.
His strong track record as a pass-catching weapon out of the backfield should make him an attractive option for other teams, especially if he's still available as injuries begin to arise during training camp.