Morant suffered the injury late in Friday's win over the Oklahoma City Thunder after getting his foot tangled with Thunder guard Lu Dort. Morant went down in immediate pain and had to be helped off the court.
Memphis is already down shooting guard Desmond Bane, who was diagnosed with a Grade 2 sprain of his right big toe earlier this week. The team said at the time he would be reevaluated in two to three weeks.
Morant, 23, is averaging 28.6 points and 7.1 assists per game this season.