The Padres placed Mize on the 15-day injured list Saturday with a sprained right ankle.
Mize struggled mightily during his start Friday against Arizona, coughing up seven runs in only four innings, and his ankle injury may help to explain his poor showing. He'll now be forced to sit out through the end of the NLDS, and the Padres will recall Griffin Canning in a corresponding move to add to their bullpen depth.