TNT's David Aldridge first reported the sides agreed to a deal that will send the No. 1 pick to Philadelphia and will be finalized Monday, and the 76ers are expected to take Washington star Markelle Fultz.
The Vertical's Adrian Wojnarowski added Philadelphia is expected to give up the third overall pick in 2017, a 2018 first-round pick from the Los Angeles Lakers and a 2019 protected first-round pick from the Sacramento Kings.
However, Wojnarowski later amended the reported return, noting that Boston will receive the 2017 pick and the 2018 pick with protections. The 2019 first-round pick from the Kings would only go to the Celtics if the 2018 pick does not convey.
76ers insider Derek Bodner clarified that Boston will receive the 2018 pick if it falls between the second and fifth pick in next year's draft.
Wojnarowski added the 76ers needed to see Fultz's private workout Saturday before completing the deal, with a call to announce the swap planned for Monday.
ESPN's Marc Stein and Zach Lowe reported Friday that the Philadelphia 76ers engaged the C's about swapping the Nos. 1 and 3 picks, possibly with more selections involved, and Wojnarowski added that the Sixers had an eye toward Fultz.
In addition to the Sixers, the Lakers wanted the No. 1 overall pick after Fultz's workout blew them away, per Jonathan Givony of Draft Express.
Wojnarowski added Saturday that while the Lakers were interested in a deal, the 76ers provided too many first-round picks for Los Angeles to compete with.
Givony reported the Lakers were considering sending the No. 2 overall pick and forward Julius Randle to Boston for No. 1.
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The multiple trade reports surfaced after ESPN's Chad Ford wrote that Fultz wasn't necessarily a lock for the Celtics with the top pick.
Ford noted Boston was looking at other options, and specifically mentioned Kansas swingman Josh Jackson.
In terms of what they need, Jackson may be a better fit for the Celtics than Fultz, as they already have a loaded backcourt with Isaiah Thomas, Avery Bradley and Marcus Smart.
By trading the No. 1 overall selection, the Celtics are taking a huge risk, as Fultz dominated to the tune of 23.2 points, 5.9 assists, 5.7 rebounds, 1.6 steals and 1.2 blocks per game in his one season at Washington.
If Boston likes Jackson or Lonzo Ball similarly to Fultz, however, the move makes sense in terms of landing another top prospect and additional assets.
From Philadelphia's perspective, the trade allows it to add another top-flight prospect to a team that already includes Ben Simmons, Joel Embiid and Dario Saric.
While Simmons and Embiid have struggled to stay healthy, the addition of Fultz would give the 76ers perhaps the best stable of young talent the NBA has seen in years.