WASHINGTON — The Knicks won at basketball but lost at ping pong and, more importantly, lost their best player. RJ Barrett, the emerging face of the franchise, suffered a “sprained knee” in the second quarter of Friday night’s 114-92 victory over the Wizards, according to the team. Barrett was injured while driving on two Wizards defenders, landing awkwardly as his right leg bent inward. He picked up an impressive assist on the play to center Jericho Sims, but quickly walked off the court while clutching his knee. Barrett never returned to the bench as the Knicks ran away with the victory behin…