The Boston Celtics acquired guard Josh Richardson in a trade with the Dallas Mavericks. Richardson averaged 12.1 points and 2.6 assists per game in 59 games for Dallas last season. Brandon Wade/Associated Press

BOSTON — The Boston Celtics acquired guard Josh Richardson from Dallas on Saturday, a move that gives the Mavericks salary cap flexibility while adding young center Moses Brown.

The trade involves teams with new leaders in the front office. Brad Stevens recently became Boston’s president of basketball operations after eight seasons as coach, ending Danny Ainge’s 18-year run in charge of personnel.

Nico Harrison is the new general manager and president of basketball operations in Dallas after nearly two decades in which Donnie Nelson held one or both of those titles. Owner Mark Cuban fired Nelson in June, and Rick Carlisle resigned as coach a day later. Jason Kidd replaced Carlisle.

The Mavericks got Richardson in a trade with Philadelphia last offseason, hoping his defense would boost the Luka Doncic-led club. A solid start was interrupted by a COVID-19 absence before Richardson was relegated to the bench late in the regular season and for the first-round playoff loss to the Los Angeles Clippers.

It will be the fourth team in four years for Richardson, who was drafted in the second round by Miami in 2015 and spent four seasons with the Heat. Richardson exercised his $11.6 million player option as part of the trade.

With that money off the books, the Mavericks should have about $30 million in cap space. They have interest in re-signing guard Tim Hardaway Jr., who came to them along with Kristaps Porzingis in the blockbuster trade with New York in 2019.

The Celtics used what was left of their trade exception from the Gordon Hayward deal with Charlotte, about $10.9 million. The Mavericks are getting a trade exception of the same value, which could give them more flexibility in free agency.

The 7-foot-2 Brown averaged 8.6 points and 8.9 rebounds in 43 games with Oklahoma City last season. It will be the third team in three NBA seasons for Brown, who went undrafted in 2019 after his freshman season at UCLA.