Leonard has been in New York since Monday, and there's no timetable set on a possible return to San Antonio, sources said.
Time is running out on Leonard's chances of returning to the active roster this season, and optimism has waned that Leonard will play in any of the Spurs' six remaining regular-season games or join them in the Western Conference playoffs.
The Spurs are 44-32 and fourth in the Western Conference playoff standings.
Spurs staff has traveled to New York to meet with Leonard and stay abreast of his treatment and activity, sources said. Leonard has been using the National Basketball Players Association headquarters gymnasium facilities in recent days, sources said.
This is Leonard's second extended trip to New York to consult with his own outside medical team and work out at the NBPA's Manhattan facility. He spent an extended period in New York prior to the February All-Star break.
Leonard, 26, is a two-time All-NBA Defensive Player of the Year, two-time Defensive Player of the Year and MVP of the 2014 NBA Finals. He's considered one of the league's elite two-way players. Leonard is eligible for a five-year, $217 million super max contract extension this summer with the Spurs. He could become a free agent in the summer of 2019.
Leonard left San Antonio and his teammates in the aftermath of increasing tension levels surrounding his disconnect with the team and several near-returns that resulted in Leonard backing off and staying on the sidelines. Leonard's status was the focus of a Spurs player-only meeting on March 17, league sources told ESPN, and prominent teammates Manu Ginobili and Tony Parker have drawn attention for public comments about Leonard's status.
"I've been through it," Parker said recently. "It was a rehab for me for eight months. Same kind of injury, but mine was 100 times worse, but the same kind of injury. You just try to stay positive."
In the aftermath of the team meeting, Ginobili told reporters that the Spurs needed to proceed as though Leonard would not be returning to play with them.
"He is not coming back," Ginobili said. "For me, he's not coming back, because it's not helping [to think Leonard is returning]. We fell for it a week ago again. I guess you guys made us fall for it. But we have to think that he's not coming back, that we are who we are, and that we got to fight without him. That shouldn't be changing, at least until he is ready for the jump ball."
Leonard stepped away to focus on rehabbing the injured quad after a nine-game return to the Spurs that ended on Jan. 13. In limited minutes in Leonard's nine games this season, he averaged 16.2 points and 4.7 rebounds a game.
Parker, meanwhile, has recovered from a ruptured left quadriceps tendon suffered last May, making his season debut in November after 208 days. Parker's injury was considered more significant than Leonard's, and the team sought the expertise of the world's best tendon experts in both cases. Parker elected to utilize the Spurs' doctors while Leonard sought consultation outside the organization, which is a practice the franchise encourages as its goal is to protect the player's long-term future.
"Tony exhibited great trust in our whole process from the very beginning because of the lack of historical knowledge of this," Spurs general manager R.C. Buford told ESPN's Michael C. Wright recently. "I was anxious to make sure that we got the world's best experts engaged before the surgery started. And Tony made a comment to me as we were analyzing resources, 'I've trusted Dr. [David] Schmidt my entire career, and why would I want to trust anybody else?'"
Leonard initially sought treatment within the organization before consulting with a specialist in New York on Jan. 16. Leonard informed the Spurs on Jan. 17 that he needed to take time away to focus on rehabilitation.
Leonard resumed working out in San Antonio on Feb. 27, and the intensity of his workouts have varied. On occasions in the past month, Leonard has increased his workout load in preparation to return to the floor, only to step back and conclude he wasn't prepared to do so.
"Sometimes you feel like an alien to the core group and you've got to fight through it," Ginobili said. "You've got to make an effort to still be around, and be part of the everyday topics; the good things and the bad things. You've got to make an effort."
Spurs coach Gregg Popovich was asked whether the team is making an effort to keep Leonard engaged and feel as if he's a part of the team.
"It's the same as a player who is the 13th man sitting on the end of the bench," Popovich said. "The more you're participating, the more you feel like you're a part of the deal. But anybody who's injured, sitting on the bench or not playing, feels a little bit different, of course. That's just human nature. "He's a nice guy. I love the kid. What am I gonna do? Sometimes he wants to rehab in the room, getting stronger; use the time wisely instead of watching us out there."