WASHINGTON — As if enough things weren’t going wrong for the Mets these days, left fielder Fernando Tatis (pictured) suffered a separated right shoulder in the fifth inning tonight when he dived for a sinking liner by the Nationals’ Odalis Perez. Tatis left the game immediately and was replaced by Nick Evans. There is no word yet on how long Tatis will be sidelined. Tatis was hitting .299 with 11 homers and 47 RBIs going into tonight’s game.