Richardson will exercise his $11.6M option in order to make the deal happen, Charania adds.
The Celtics are using a $11.05M trade exception acquire in the Gordon Hayward sign-and-trade last year in order to make the deal, Bobby Marks of ESPN tweets. Richardson made $10.86M this past season, so Boston will finalize the deal on Saturday before the league calendar flips. The Mavericks will generate a trade exception in the same amount.
Dallas could have up to $33M in cap room entering free agency, though a majority could come at the cost of its own free agent Tim Hardaway Jr., Marks adds.
Richardson averaged 12.1 PPG and 2.6 APG in 59 regular-season games with Dallas this past season, including 56 starts. He’s a career 35.8% 3-point shooter and 83.2% free throw shooter with the reputation of being a quality perimeter defender.
The Celtics also agreed to a three-way deal on Friday in which they shipped big man Tristan Thompson to the Kings and acquired guard Kris Dunn from the Hawks. However, Dunn could be moved as part of another trade, according to Adam Himmelsbach of the Boston Globe (Twitter link).