WASHINGTON — Until a few days ago, the Phillies didn’t know for sure if Zach Eflin would be able to pitch Sunday. In hindsight, he probably shouldn’t have. Eflin left early from a start last week when his right knee stiffened. He underwent a series of tests that didn’t reveal new damage to his twice surgically repaired patellar tendon, and team doctors cleared him to start, as scheduled. But Eflin had trouble keeping the ball down in the zone, gave up four runs, and exited after only two innings in the Phillies’ sweep-spoiling 9-3 loss to the Washington Nationals. An update wasn’t available du…