Trail Blazers get: Enes Kanter
Grizzlies get: Mario Hezonja, 2020 first-round pick (No. 30: Desmond Bane)
Celtics get: Future draft considerations
Portland Trail Blazers: B

I've been touting Kanter's return to the Blazers as a sensible outcome for some time now. Given both Jusuf Nurkic and Zach Collins are coming off injuries, and Portland seems to prefer Collins playing power forward, there was an opening for a reliable backup center. I viewed a Kanter trade as a vehicle to add one of the three Celtics' first-round picks, but getting him for free is still useful.
We already know how well Kanter works in the Blazers' system from his key role in the team's run to the 2019 Western Conference finals. Signed to back up Nurkic after being waived by the New York Knicks after the trade deadline, Kanter ended up moving into the starting lineup a month later when Nurkic suffered a horrific compound lower left leg fracture. Kanter started 14 of 16 games for Portland in the playoffs, averaging 11.4 points and 9.7 rebounds per game.
Because the Blazers had only non-Bird rights on Kanter as an unrestricted free agent last summer, he got away to Boston and the team brought in Hassan Whiteside to cover Nurkic's extended rehab. As a stopgap, that work moved fine, but Whiteside was less effective after Nurkic's return in the bubble. During Portland's first-round series loss to the Los Angeles Lakers, the Blazers were minus-22 in Whiteside's 106 minutes. With Whiteside now a free agent, Kanter returns as a better fit at backup center.
Thanks to a trade exception created in the Kent Bazemore-Trevor Ariza deal, Portland could take on Kanter's salary without having to match it. Sending out Hezonja, who picked up his player option earlier this week, does offset a bit of Kanter's $5 million salary and creates an extra roster spot for the Blazers.
Even after adding Covington and Kanter in trades, Portland is still $25 million below the luxury-tax line, giving the Blazers plenty of flexibility to use both their $9.3 million non-taxpayer midlevel exception and their $3.6 million biannual exception to further upgrade the bench. A strong individual defender with size on the wing, like Justin Holiday, would be an ideal addition for Portland if Rodney Hood is heading elsewhere after declining his $6 million player option.
Boston Celtics: A-

Back when we expected Gordon Hayward to pick up his $34.2 million player option, moving Kanter looked imperative for the Celtics to cut their luxury-tax bill. Now, the situation is a bit more complicated, although Boston is probably better off without Kanter either way because the Williamses (Robert and Grant) are capable of playing backup minutes at center.
The luxury tax could still be something of a concern if the Celtics bring Hayward back on a new, long-term deal or end up sending him to a team over the salary cap in a sign-and-trade. Even if Hayward signs with a team that has the cap space to do so, Boston would be wise to make a sign-and-trade worth the other team's while so as to create a trade exception for the value of Hayward's 2020-21 salary. (That would be in addition to a smaller exception for Kanter's $5 million salary generated in this trade, although the two can't be combined.)
Additionally, moving Kanter's salary didn't appear quite as costly as I thought. The Celtics were also able to get future seconds in return for the 30th pick, which they almost had to move because of a roster crunch. Including Daniel Theis, whose salary becomes guaranteed on Saturday, Boston has 11 guaranteed contracts with this year's No. 14 (Aaron Nesmith) and No. 26 (Payton Pritchard) picks. The Celtics also have Javonte Green and Semi Ojeleye on non-guaranteed contracts and would presumably like to re-sign guard Brad Wanamaker, which would put them at 14 players before re-signing or replacing Hayward.
Memphis Grizzlies: B

The inclusion of Kanter, who hadn't yet picked up his player option for 2020-21, was always a logical explanation of why we hadn't heard details of Memphis' deal to add the 30th pick on draft night beyond a pair of second-round picks. Kanter didn't make sense for the Grizzlies, who are flush at center with Jonas Valanciunas, Jaren Jackson Jr. and Brandon Clarke all capable of playing there. By flipping him for Hezonja, Memphis has come out ahead financially.
Beyond that, a couple of second-round picks is a reasonable price for the Grizzlies to move back into the first round -- having sent Boston the No. 14 pick to complete the long-ago Jeff Green trade -- and take Bane, who rated 28th in my consensus projections.