The Canadian Football League team announced the five-foot-eight, 206-pound running back will miss the rest of the playoffs with a broken left ankle.
Kackert, the MVP of Toronto’s Grey Cup win over Calgary last November, suffered the injury at Friday’s practice and had surgery Tuesday.
His season has been plagued with knee and shoulder injuries in addition to a concussion.
Kackert, who re-signed with the Argos last off-season, was the club’s top rusher in the regular season, racking up 480 yards on 71 carries for a 6.8-yard average with three touchdowns.
He had his most productive season a year ago, rushing for 638 yards on 100 carries with five TDs.
Toronto hosts the Hamilton Tiger-Cats in Sunday's CFL East final (1 p.m. ET).