The Dolphins placed Duck (knee) on injured reserve Tuesday.
Duck suffered a season-ending knee injury in Sunday's win over the Falcons. In addition to placing Duck on injured reserve, Miami signed CB Ethan Robinson to the practice squad and placed CB Kendall Sheffield (undisclosed) on the practice-squad injured list. With Duck done for the year, Jack Jones, JuJu Brents, Rasul Douglas and Ethan Bonner should handle the bulk of the cornerback duties.