The deals
Grizzlies get: Tyler Dorsey
Hawks get: Shelvin Mack, Jabari Bird
Celtics get: Protected second-round pick
Get more trade grades for every deal here
Atlanta Hawks: C
The Hawks' deadline day proved a bit of a bust. Atlanta found no takers for veterans Dewayne Dedmon and Jeremy Lin, making only a pair of minor deals involving no draft picks that will apparently result in waiving both players.
I can't really find an explanation for why the Hawks traded second-year guard Dorsey for Mack, who has a higher salary. Perhaps there's more to this trade than has been reported. The Bird deal is a more standard salary dump in which Atlanta got cash in return.
Chris Vivlamore of the Atlanta Journal-Constitution reported that the Hawks also needed to waive second-year wing Daniel Hamilton "to clear a necessary roster spot after a technical error." Presumably the Hawks intended to complete the Mack trade in time to waive him before the deadline and use that roster spot on Bird, but were unable to do so. Fortunately, Hamilton was on a one-year deal, so Atlanta could simply re-sign him if he clears waivers.
Boston Celtics: B
Bird had not joined the Celtics all season after being charged with a number of crimes in connection with a September incident of domestic violence. Boston was awaiting resolution on Bird's case, which may not happen until after the season.
Given that, trading Bird made sense for the Celtics, who were able to reduce their tax bill by $2 million as compared to simply waiving him.
Memphis Grizzlies: B
After averaging 17 minutes in the 56 games he played as a rookie, Dorsey had seen his playing time dwindle after the arrival of first-round picks Kevin Huerter and Trae Young in the backcourt, making him expendable.
Dorsey was no great shakes when he did take the court, posting a weak .494 true shooting percentage as a rookie despite making 36 percent of his 3-point attempts. Still, at age 22 (23 later this month), he's worth a look the rest of the season for a Grizzlies team that has fallen out of the playoff race.