The Boston Celtics are in the process of finalizing a deal to send Rajon Rondo to the Dallas Mavericks, according to league sources. 

Sources tell ESPN.com that the Celtics and the Mavericks have an agreement in principle to send the All-Star point guard to Dallas for Brandan Wright, Jae Crowder, Jameer Nelson and a future first- and second-round draft pick. 

The possibility exists that other players will be added to the final deal, but Rondo to the Mavericks is expected to be completed by the end of Thursday night. 

A source indicated that a “deal is on course to happen tonight.”

Rondo would join Dirk Nowitzki, Monta Ellis, Tyson Chandler and Chandler Parsons in a high-octane starting five.

Rondo is in the final year of his contract. Rondo has left little doubt in recent months that he intends to test the market as a free agent in July. However, sources say Dallas, amid growing concern about its point guard play and sensing the opportunity to acquire a top-flight player it has coveted for some time, is confident it could win over Rondo for the long term.

Boston has the necessary trade exceptions to absorb all the salaries from Dallas while potentially generating a valuable $12.9 million trade exception (Rondo’s 2014-15 salary) to help with future roster construction.

The Celtics were at the roster maximum of 15 before the trade and will need to part with additional bodies to absorb three players from Dallas.

The Mavericks were one of several teams to express interest in Rondo. The Celtics also had talked to teams such as the Sacramento Kings, New York Knicks, Los Angeles Lakers and Houston Rockets about a potential deal, according to sources.

Rondo is averaging 8.3 points and 10.8 assists this season, his ninth in the league. 

ESPNBoston.com’s Chris Forsberg contributed to this report.