Williams to Mavs in sign-and-trade, sources say

The Dallas Mavericks and restricted free agent forward Grant Williams are finalizing a four-year, $53 million contract as part of a three-team sign-and-trade agreement with the Boston Celtics and San Antonio Spurs, sources told ESPN's Adrian Wojnarowski on Wednesday.

Williams' former team, the Celtics, will receive two second-round picks in the deal, while San Antonio will receive forward Reggie Bullock from Dallas, sources said.

Dallas also will receive two second-round picks in the deal, sources said.

Williams, the 22nd pick in the 2019 NBA draft out of the University of Tennessee, has been a key part of Boston's runs to the NBA Finals and Eastern Conference finals each of the past two seasons. The burly 24-year-old forward averaged 8.1 points and 4.6 rebounds off the bench for the Celtics this past season, shooting 39.5 percent from 3-point range on 3.7 attempts per game.

And while he vacillated in and out of coach Joe Mazzulla's rotation at times this season, he returned to a big role off the bench as this year's playoffs went on, just as he did a year ago under Ime Udoka as Boston went to the NBA Finals for the first time since 2010.

Williams, with his ability to guard above his 6-foot-6 frame and knock down open 3-point shots, was one of the more intriguing restricted free agents on the market this summer, particularly for contending teams. He's a career 43% shooter on corner 3-pointers, compared to 34% on all other 3-point attempts, according to ESPN Stats & Information research.

Williams also served the Celtics well in their playoff matchups against the Milwaukee Bucks and Giannis Antetokounmpo. Per Second Spectrum, Williams has defended Antetokounmpo on 295 halfcourt matchups in the last four seasons and the Bucks have an 86.8 offensive rating when Williams is matched up with the two-time MVP during those halfcourt sets.

Williams had surgery on his left (non-shooting) hand after the season, but the Celtics said he was expected to be ready in time for training camp.

ESPN's Tim Bontemps contributed to this report.