WASHINGTON — After one of the hottest months in baseball, it suddenly feels like a battle of attrition for the New York Mets. In the last week, the Mets have lost right fielder Starling Marte and right-handed reliever Drew Smith to injuries, and closer Edwin Diaz to suspension. Monday in Washington, the Mets played without star outfielder Brandon Nimmo, who fainted in his hotel room early in the…