The Dallas Mavericks are acquiring Grant Williams from Boston in a sign-and-trade deal that includes the San Antonio Spurs, a person with knowledge of the agreement said Wednesday night.

Dallas is sending guard Reggie Bullock and a 2030 pick swap to the Spurs, while the Mavericks and Celtics will receive multiple second-round picks, according to a person who spoke to The Associated Press on condition of anonymity because no trades can be finalized before Thursday.

Williams' contract is for $54 million over four years.

The Mavericks made it clear they thought their roster needed work after missing the playoffs when the pairing of Luka Doncic and Kyrie Irving faltered in the two months after the blockbuster deal that brought Irving from Brooklyn in February.

Irving and the Mavs have agreed on a $126 million, three-year contract that should become official when free agent deals can be signed, starting Thursday. Center Dwight Powell also is set to return.

The 6-foot-6 Williams will change the look of the Dallas frontcourt with the lanky, offensive-minded Christian Wood not expected to return. The 24-year-old averaged career highs of 8.1 points and 4.6 rebounds in his fourth season with the Celtics.

Dallas wants to rediscover the defensive mentality that helped fuel a run to the Western Conference finals in 2022. But it will have to be with a new set of key defensive pieces. The departure of Bullock comes after Dorian Finney-Smith went to the Nets in the Irving deal.

Bullock averaged 7.2 points for the Mavericks last season, a drop from 8.6 in his first season in Dallas. The 3-and-D specialist shot 40% from 3-point range in the 2022 playoffs, making 2.9 per game before dropping to 1.9 at a 38% clip in the 2022-23 regular season.