Dallas received draft rights to Emir Preldžic from Washington Wizards and sent DeJuan Blair in return.
Dallas sent DeJuan Blair to Washington on July 16, 2014 in exchange for the draft rights to Emir Preldžić. This wasn't an exchange involving an NBA draft pick to be used in a later year; Preldžić's rights already existed, and he was playing outside the league. The Wizards received a center or power forward with NBA experience. Dallas received the possibility of a future arrival rather than an immediately deployable rotation player.
Blair brought known NBA rebounding and interior experience to the Wizards. He could enter Washington's roster immediately while the rights sent to Dallas would only provide on-court value if Preldžić eventually joined the league. Washington's decision had a practical short-term goal: add frontcourt depth without using a player who was already on its NBA team. The actual NBA participation from Blair is why the trade wasn't simply an exchange of unused contractual paperwork.
The key Dallas limitation was that Emir Preldžić did not come to the Mavericks as an NBA player. Owning a set of overseas draft rights can sometimes be useful as a tradable asset, but the canonical outcome doesn't establish a major later conversion from this particular set. Washington obtained the only direct NBA on-court contributor exchanged. The team grades reflect this difference, even though the rights themselves were a legitimate asset to acquire at the time.
Wizards Win. Washington gets C for acquiring DeJuan Blair and his immediate NBA frontcourt ability. Dallas receives D because the rights to Emir Preldžić never became playing time for the Mavericks. The Wizards obtained the stronger practical return without needing to rely on an unrelated future draft selection.