Two teams in the heart of the National League wild-card race but struggling to keep pace will open a key three-game series Monday night when the visiting Washington Nationals take on the San Francisco Giants. Both teams flew into San Francisco on Sunday night after losing games that cost them series, the Nationals dropping a 7-5 decision at Arizona while the Giants were falling 6-2 at Colorado. The Nationals are tied with Philadelphia for the second wild-card spot, with the Giants residing in a tie with Arizona a half-game behind Milwaukee.