The Boston Celtics are keeping their top-five players "off limits" during trade discussions for San Antonio Spurs star Kawhi Leonard, ESPN's Adrian Wojnarowski reports.

"Boston's really got their top-five players off limits," Wojnarowski said on ESPN's SportsCenter. "Boston is more willing to do a deal that's pick-heavy. The Spurs want good players back. They don't want to rebuild. They want picks and they want guys who can help them stay in the playoffs."

Though Wojnarowski does not clarify who the "top-five players" are, it's safe to assume he's referring to the 2018-19 projected starting lineup of Kyrie Irving, Jayson Tatum, Jaylen Brown, Gordon Hayward and Al Horford. The Celtics, however, have a trove of draft picks, including up to four next summer.

They have their own pick, the Sacramento Kings' (top-one protected), the Memphis Grizzlies' (top-eight protected) and the L.A. Clippers' (top-14 protected). The Celtics also have other potentially enticing trade pieces, such as point guard Terry Rozier or forward Marcus Morris, both of whom are on inexpensive deals. They do, however, each become free agents in 2019, when Horford and Irving can hit free agency, as well.

Not including any of their best guys -- and thus, not including any large salaries -- means the Celtics would have to deal at least five players to match salaries in any possible trade for Leonard, who makes $20.1 million in 2018-19 and has a 15 percent trade kicker (which means his salary gets a 15 percent bump if he's dealt). It would make for quite the busy deal.

Leonard, who wants the Spurs to trade him, has reportedly made it clear that he prefers to head to the Los Angeles Lakers. And considering he also becomes a free agent in 2019, he holds much of the leverage in this situation. The Celtics or Philadelphia 76ers, who are also reportedly in discussions with the Spurs, don't want to give up a future-altering haul only for Leonard to leave them for L.A. next summer. The 76ers are keeping All-NBA center Joel Embiid, Rookie of the Year Ben Simmons and 2017 No. 1-overall pick Markelle Fultz off the table in talks with the Spurs, Wojnarowski said on SportsCenter.

The Lakers, however, seem to be moving slowly.

"The Lakers now, in the way they've approached these trade talks with San Antonio, they're kind of showing their hand that they may be willing to wait until next summer in free agency," Wojnarowski said. "They've not made an overwhelming offer. I don't think they've come close to meeting the threshold that the Spurs have."

San Antonio can still offer Leonard a five-year, max extension which would start in 2019-20 and projects to be worth about $219 million. No other team could give him such a large contract in 2019 free agency.

The hesitancy on dealing for Leonard, however, is not just because of his impending free agency. The 2014 NBA Finals MVP played only nine games this past season because of a leg injury. Potential trade partners are yet to see his medical reports, which could be confusing from the start. The Spurs' tiff with Leonard stems from when team doctors cleared him to return, but he declined to do so because his own private doctors advised him against it.

Leonard, a two-time Defensive Player of the Year, averaged 25.5 points, 5.8 rebounds and 3.5 assists during 2016-17, his most recent healthy season. He finished third in MVP voting that year.

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Fred Katz covers the Celtics for MassLive.com. Follow him on Twitter: @FredKatz.