(Sports Network) - In the heat of a pennant race, the National League East- leading New York Mets will send Jonathon Niese to the mound tonight for his major league debut against the Milwaukee Brewers at Miller Park.

Niese is taking the roster spot currently vacated by John Maine, who is on the disabled list with a bone spur in his right shoulder. Niese, a 21-year-old left-hander, went 5-1 with a 3.40 ERA with Triple-A New Orleans. He also saw action at Double-A Binghamton this year.

The seventh-round pick in 2005 is known for a looping curveball similar to what San Francisco left-hander Barry Zito throws. Niese made three starts for the Mets during spring training and pitched to a 3.12 earned run average. He will get a taste of Milwaukee's solid lineup on Tuesday night.

New York pushed its lead in the East standings to two games over the Philadelphia Phillies after a 4-2 win over the Brewers in Monday's series opener. Carlos Delgado put the Mets ahead for good with a two-run homer in the eighth inning and ended with two hits.

Jose Reyes, Daniel Murphy and Carlos Beltran also added a pair of hits apiece for the Mets, who have won four of their last five games.

Delgado's 20 home runs and 60 RBI since June 27 are the most in the National League.

Mets starter Johan Santana limited the Brewers to a pair of runs on seven hits, while walking one and matching a season-high with 10 strikeouts over six innings. The lefty took a no-decision and ran his unbeaten streak (5-0) to 12 starts. Nelson Figueroa was credited with the win after pitching one-plus innings of relief.

The Mets are 4-2 on an eight-game road trip and 36-36 away from Shea Stadium this season.

Milwaukee still leads the NL Wild Card race by 5 1/2 games over the Phillies and sit 4 1/2 games back of the Chicago Cubs in the Central standings. It entered this series with New York fresh off a three-game sweep of the Pittsburgh Pirates, but lost starter Ben Sheets after the fifth inning with tightness in his left groin on Monday.

The right-hander had a 1-0 lead before his departure, having given up only two hits and one walk. Eric Gagne was saddled with the loss for allowing three runs in the eighth.

Ryan Braun had three hits and an RBI in a losing cause for the Brewers, who are 0-1 on a 10-game homestand and 41-25 at Miller Park this year.

Milwaukee hopes that Manny Parra can break out of his current funk when he toes the rubber on Tuesday. Parra is just 1-4 over his past seven trips to the mound and did not factor in a 5-3 loss at St. Louis on Wednesday.

Parra held the Cardinals to a run on six hits in six frames to remain 10-6 on the season, while lowering his earned run average to 4.00 in 27 games (26 starts).

The left-hander, who is 6-2 at home this season, will face the Mets for the second time in 2008. In a 4-2 setback on April 11 at Shea Stadium, Parra allowed three runs and six hits in four innings to absorb the loss. He is 0-1 with a 3.48 ERA in two career games, one of which was a start, versus New York.

Milwaukee won two of three games against the Mets at Shea Stadium from April 11-13 this season.