The 23-year-old originally injured his hand on Dec. 9. He had X-Rays the next day and missed two games, then returned to play two before sitting out the next four.
On Sunday, Leonard got an injection in his hand, after which Spurs head coach Gregg Popovich said there is no timetable for the forward's return.
Popovich also called the injury "very problematic."
Leonard is averaging 15.2 points, 7.6 rebounds and 2.5 assists this season for San Antonio (18-11), who face the Oklahoma City Thunder on Christmas Day.
- Molly Geary