Leonard has not practiced since training camp began but has been rehabbing at the Spurs' practice facility.
Popovich also said he was unsure of when Leonard might return.
"I don't gauge it," Popovich said. "He's still rehabbing and when he's ready, he'll be ready. I try not to qualify it."
The 26-year-old Leonard missed time in the 2017 playoffs due to an ankle injury suffered in Game 5 of the Western Conference semifinals against the Houston Rockets. He aggravated that sprain in Game 1 of the conference finals and sat out the rest of San Antonio's 4-0 series loss to the Golden State Warriors.
Earlier in training camp, Popovich said the injury was not recent but a continuation of an issue that first occurred sometime last season.
The 6-foot-7, 230-pound Leonard is entering his seventh NBA season after averaging a career-high 25.5 points and 5.8 rebounds last season, making the All-Star Game for the second time in his career. He was voted first team All-NBA and named first team All-Defense.