On The Lowe Podcast, ESPN's Zach Lowe said the Spurs wanted "one of the two big guys" in a potential trade, referring to Joel Embiid and Ben Simmons.
"There is no evidence that the Spurs wanted [Markelle] Fultz," Lowe said on his Lowe Post podcast. "I've been told the Spurs never asked for Fultz, and actively didn't want Fultz, and in fact wanted one of the two big guys."
San Antonio's haul for Leonard ultimately proved to be much lower than its aim. They got DeMar DeRozan, Jakob Poeltl and a 2019 first-round pick from the Toronto Raptors in exchange for Leonard and Danny Green.
The Sixers were never going to consider trading Embiid or Simmons for Leonard. The entire point of their interest in Leonard was building a title contender around Embiid and Simmons, a pair of burgeoning stars in their 20s who should be the foundation of their team moving forward. Adding Leonard might have made Philadelphia the Eastern Conference favorite in 2018-19.
A more realistic package could have included Dario Saric, Robert Covington and perhaps Markelle Fultz, but Lowe indicated the Spurs had no interest in Fultz. San Antonio's front office clearly wanted a proven player who could perform right now rather than pieces for a rebuild—a questionable move at best.
The Spurs as they stand are a borderline playoff team. They could have expedited an inevitable rebuild had they accepted a package built around younger talent.
As it stands, it seems unlikely that the Spurs and Sixers ever got too deep into conversations if Simmons or Embiid was the starting point.