The 26-year-old has been the club's lead back for the past two seasons, but the NFC West side selected Johnson in the third round of the Draft to provide competition in the backfield.
Ellington, who missed the last month of the season with a hernia problem, believes that Johnson will ease the burden on him and improve the Cardinals' offense.
When asked if the addition of Johnson was a positive move for him, Ellington told reporters: "I don't see why not. It allows me to have more rest time, and it should keep the offense upbeat."
Ellington recorded 1,055 yards from scrimmage for the Cardinals last season, scoring five touchdowns.