DeJuan Blair, left, will join the Wizards, reportedly on a three-year contract. (Tony Gutierrez/Associated Press)

The Washington Wizards have completed a sign-and-trade deal with Dallas to acquire free agent forward/center DeJuan Blair for the rights to 2009 second-round draft pick Emir Preldzic, the team announced Wednesday night.

By using a portion of one of their three trade exceptions in hand, the Wizards brought in the 6-foot-7, 270-pound Blair on a three-year contract worth $6 million, according to multiple sources with knowledge of the situation. The move comes a day after Washington brought in forward Kris Humphries from Boston for part of a trade exception obtained in the three-team deal that sent Trevor Ariza to Houston.

The Wizards have been in talks with the Mavericks about landing Blair since earlier this week, according to a source. Blair, a burly post player who averaged 6.4 points and 4.7 rebounds per game as a reserve on the Mavericks last season, tweeted a reference to his new home Wednesday afternoon.

In Blair, the Wizards add another piece to what’s become a deep, experienced bench heavy on front-court support, including Humphries and Drew Gooden, who was brought back on a one-year deal Tuesday. Drafted out of Pittsburgh by the San Antonio Spurs with the No. 37 pick in 2009, Blair has developed into a dependable and physical post presence in five seasons with the Spurs and Mavericks, though he is far from swift after undergoing major surgery on both knees.

“DeJuan gives us a tough inside presence who can score and rebound at both front court positions,” Wizards President Ernie Grunfeld said in a statement. “His addition makes our bench even deeper and will allow us to be flexible with our lineups.”

The 25-year-old Blair came up big against his old team in the first round of last season’s Western Conference playoffs, averaging 6.7 points, 6.3 rebounds and two steals off the bench to help Dallas push the eventual champion Spurs to seven games.

In exchange for Blair, the Wizards shipped away Preldzic, a Turkish player who after being drafted by Phoenix with the No. 57 pick in 2009, has never played a NBA game. The Suns traded the 6-foot-9 swingman to Cleveland, which later shipped him to the Wizards as part of the 2010 deal that sent Antawn Jamison to the Cavaliers.

The acquisition of Blair, who played on a one-year minimum contract last season, creates some uncertainty for the future of forward Kevin Seraphin. The Wizards extended a qualifying offer of $3.8 million to Seraphin, who has spent his entire four-year career in Washington but the France native said, “I want to play, too, so we’ll see,” following his exit interview in May.

With Blair in the fold, the Seraphin offer on the table and the deals for Humphries, Gooden and Paul Pierce expected to be finalized in the near future, the Wizards technically have accounted for 14 of their 15 roster spots. Free-agent guard Garrett Temple could be brought back to fill that final vacancy, but another spot is expected to open up when Melvin Ely, whose non-guaranteed contract was acquired from New Orleans in the Ariza deal, is cut loose, according to sources with knowledge of the situation.