(Sports Network) - The New York Mets' late collapse last season has been well- documented. It seems another could be on its way for the club, which resumes a four-game series tonight against the host Washington Nationals.

The Mets suffered their third straight loss and fourth in five tries after Tuesday's 1-0 setback in the second test of this series at Nationals Park. Mets starting pitcher Mike Pelfrey absorbed the tough-luck loss, surrendering one run on seven hits in seven frames. He also walked four batters and struck out four for the Mets, who fell a half-game behind the Philadelphia Phillies for the top spot in the NL East standings.

Mets left fielder Fernando Tatis left Tuesday's loss with a separated right shoulder and will miss the rest of the season. Tatis will be missed by the team after he batted .297 with 11 homers and 47 RBI in 92 games this season.

New York owned a seven-game lead in the East with 17 games to go last season, but went 5-12 over that stretch to fall out of the playoff picture. The slump carried over into the 2008 campaign and manager Willie Randolph was fired in June. Jerry Manuel has done a solid job since as interim skipper.

On a more positive note, the Mets are a half-game ahead of the Milwaukee Brewers in the NL Wild Card standings.

New York hopes Brandon Knight can keep it in playoff contention this evening when the youngster toes the rubber. Knight is 0-0 with a 6.43 ERA in three games (1 start) this season.

He last took the hill in a 10-8 win versus Washington on September 9, when he allowed a run on one hit and a walk in just an inning of work. Knight's first career start was on July 26 versus St. Louis, and he was reached for four runs and seven hits in five frames of a 10-8 New York loss.

Washington will try for its third straight win tonight after taking the first two matchups of this set. Nats starter Odalis Perez hurled 7 1/3 shutout innings and allowed four hits, fanned six batters and did not issue a walk for the win. Cristian Guzman finished 2-for-4 and knocked in the lone run for the Nationals, who entered this series on a five-game slide.

Taking the ball for the Nationals on Wednesday will be Shairon Martis, who will make the third start of his career. Martis will face his third straight NL East opponent, having made his debut on September 4 at Atlanta. He suffered the loss after giving up two runs in five innings.

Martis then took the hill last Friday at Florida and yielded two runs -- one earned -- over five innings in a 2-1 loss. The right-hander is 0-2 with a 2.70 earned run average to begin his major league career.

The Mets are 10-6 against Washington this season and 4-3 at Nationals Park. New York had won the last five matchups in the series before Monday's loss in the series opener.