Head coach Gregg Popovich said Wednesday he would be surprised to see Leonard back on the floor this season, according to Michael C. Wright of ESPN.
"We've got to move on," Popovich added, per Wright.
Leonard last appeared in a game on Jan. 13, and Adrian Wojnarowski of ESPN.com reported the playmaker "bears the burden of determining when he's prepared to play again."
According to Wojnarowski, Leonard consulted with a specialist for another opinion on his injured quadriceps and "has elected against returning to the active roster" even though he was medically cleared to return.
"If by some chance he is, it's gonna be pretty late into the season and it's going to be a pretty tough decision; how late to bring somebody back," Popovich said, per Wojnarowski. "So that's why I'm just trying to be honest and logical. I'll be surprised if he gets back this year."
Wojnarowski noted "the injury, rehabilitation and timetable for a return has complicated the Spurs and Leonard's relationship, causing tension and fraying the fabric of what was once a strong partnership."
This is another setback for Leonard in an injury-ravaged season. He suffered a partial tear in his left shoulder in mid-January, and he missed the start of the campaign because of the quadriceps injury.
In November, Popovich said he had "never, never" seen an injury like the quad one Leonard suffered, per Wright.
"What's really strange is that [point guard] Tony [Parker] has the same injury, but even worse," Popovich continued. "They had to go operate on his quad tendon and put it back together or whatever they did to it. So to have two guys, that's pretty incredible. I had never seen it before those guys."
While the Spurs have remained afloat even with Leonard sidelined for all but nine games, it's difficult to envision them winning this year's NBA championship without their go-to scorer and defensive leader.
Leonard already has two Defensive Player of the Year awards, an NBA Finals MVP and two appearances on the All-NBA first team on his resume. He averaged a career-high 25.5 points, 5.8 rebounds and 1.8 steals per game last season.
The Spurs likely would have called upon him to guard the likes of James Harden, Stephen Curry, Klay Thompson and Kevin Durant in critical moments of postseason series. Instead, it appears as though they'll have to turn elsewhere.