WHO: Dallas Mavericks forward P.J. WashingtonWHAT: A clutch performance in the NBA’s Western Conference SemifinalsWHY IT’S SO GREAT: In February, the Mavs made what fans worried was a desperation move: trading a top-two protected first-round draft pick and two players to the Charlotte Hornets for Washington and a pair of second-round picks. ESPN, grading the trade, gave the Mavs a D on their decision-making, with NBA analyst Kevin Pelton offering a brutal assessment: “The question here is what problem Washington is solving. Five years into his career, I’m still not sure what Washington is as an NBA player.” (The Hornets, meanwhile, got an A for getting a valuable return for Washington, who wasn’t even a full-time starter in Charlotte.) Dallas fans were even more upset. A…