Sources: Grant Williams heading to Mavs in sign-and-trade - ESPN

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.

San Antonio will receive forward Reggie Bullock and an unprotected first-round pick swap in 2030 from Dallas, while both the Celtics — Williams' former team — and the Mavericks will receive two second-round picks, sources said.

The Celtics also will get a $6.2 million trade exception, per ESPN's Bobby Marks.

Acquiring Williams, a burly 24-year-old who averaged 8.1 points and 4.6 rebounds off the bench for the Celtics this past season while shooting 39.5 percent from 3-point range on 3.7 attempts per game, gives Dallas a young, versatile 3-and-D forward who should be a perfect complement to the Mavericks' star-studded backcourt of Luka Doncic and Kyrie Irving.

And, by acquiring Williams in a sign-and-trade, Dallas still has access to its full mid-level exception, giving it an option to add another significant piece in free agency. Sources have told ESPN's Tim MacMahon that Dallas has interest in Portland Trail Blazers restricted free agent forward Matisse Thybulle.

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. 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.

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