Along with that, the Celtics are including a first-round pick in the deal, according to Chris Haynes of Yahoo Sports.
White, 27, is averaging is averaging 14.4 points, 3.5 rebounds and 5.6 assists in 49 games, and is widely considered one of the league’s best perimeter defenders. His outside shot, however, remains a bit shaky — as he’s making just 31 percent of his 3-point attempts.
Richardson, 28, is in his first year with the Celtics and has been experiencing a basketball rebirth of sorts, averaging 9.7 points in 44 games. He could team well with Spurs star guard Dejounte Murray.
Richardson is due to earn about $12.4 million next season, the final year of his deal. Along with the Celtics and Mavericks, he has also spent time with the 76ers and Heat.
Langford, 22, had had a rocky start to his career in Boston, and is averaging 4.7 points in 44 appearances. Perhaps the Spurs will offer him an increased opportunity.