(Sports Network) - Mike Pelfrey has been pitching like an ace lately. The New York Mets will need that trend to continue tonight, if they want to hang onto first place in the NL East heading into their two-game showdown with the Philadelphia Phillies at Citizens Bank Park on Tuesday.

First things first, though, as New York turns to Pelfrey to snap a two-game losing streak in the finale of its four-game series with the Houston Astros at Shea Stadium.

The Mets saw their division lead dwindle to a half-game on Sunday, as Brad Ausmus and Darin Erstad each homered in the 10th inning to give Houston a 6-4 win.

Ausmus had just one home run coming into the game, and Erstad had hit only two. But the two delivered against Pedro Feliciano in the top of the 10th. Leading off the frame, Ausmus drove a pitch high to left field that just cleared the fence.

Feliciano rebounded to strike out Michael Bourn and got pinch-hitter Lance Berkman to fly out. That brought up Erstad, who slugged the ball over the right-field wall for a two-run cushion.

Jose Valverde then set the Mets down in order in the bottom half of the 10th to seal the win and nail down his 33rd save of the season.

Feliciano (2-4) took the loss for New York, while LaTroy Hawkins (3-1) got the win after pitching a perfect ninth for Houston.

Erstad finished with two hits, while Hunter Pence hit a two-run homer -- his career-high 18th of the season -- for Houston. Starter Randy Wolf gave up four runs on seven hits and three walks in six innings of work for the Astros.

Carlos Beltran hit a pair of homers for the Mets in the loss. Oliver Perez allowed four runs on four hits and a walk in 6 1/3 frames, while striking out eight for New York, which had won four straight prior to its consecutive losses to the Astros.

Pelfrey has been tremendous for the Mets and is coming off his first complete- game win. He went the distance against Atlanta on Wednesday, allowing three runs and three hits to run his record to 12-8 on the year and lower his earned run average to 3.86.

The 24-year-old righty has won 10 of his last 12 decisions.

Pelfrey has faced the Astros three times in his young career and is 1-2 with a 6.32 ERA against them.

Houston will counter with right-hander Brian Moehler, who is 9-4 with a 3.87 ERA. Moehler won his fifth straight decision Tuesday in Milwaukee, holding the Brewers to two runs (1 earned) and nine hits in 5 1/3 frames.

Moehler is 2-4 lifetime against the Mets with a 3.03 ERA in seven games, four of which were starts.

Prior to these last two wins, the Astros had lost four straight and six of their last seven contests at Shea Stadium.