Nationals face another left-hander versus Mets

Success against southpaws is a huge reason the Washington Nationals have the best record in the majors, as they continue to occupy first place in the NL East.

The Nats will face their second left-hander in as many nights when they battle Jonathon Niese in the second test of a three-game series versus the New York Mets.

The Nationals are 23-5 in games started by opposing left-handed starters this season.

Niese aims to build on his strong start Sunday night against the Atlanta Braves. The Mets lefty allowed one run over eight innings in a 6-5 win. Niese has faced the Nationals five times, going 2-0 with a 2.93 ERA.

Edwin Jackson looks push his 2012 record above .500 for the Nationals. The right-hander was tagged for five runs on eight hits in 5 2/3 innings, but he got a winning decision in a 6-5 final at Arizona a week ago. He's 1-0 with a 5.29 ERA in three games versus the Mets.

Last night, Michael Morse belted a grand slam and Bryce Harper added a two-run homer as the Nationals won, 6-4. Morse is riding a 13-game hitting streak.

Ross Detwiler (7-5) threw six quality innings, allowing three runs on six hits for Washington, which was coming off a successful 8-2 road trip.

Johan Santana (6-9) tumbled to a fifth straight loss after surrendering six runs on seven hits over five innings.

Santana, who lasted a career low-tying 1 1/3 innings in his previous start, retired the first nine batters after being staked to a lead on Daniel Murphy's two-run single in the first frame.

But the Nationals, perhaps sluggish following just their second off day since the All-Star break, woke up in the fourth with three straight singles by Jayson Werth, Harper and Ryan Zimmerman.

Morse, hitless in his previous nine at-bats against Santana, made it four hits in a row when he went the other way with a letter-high fastball and found the right-field seats for the Nationals' first grand slam of the season.

"We had a good plan coming in, I felt pretty good," Santana said. "I was commanding my fastball better tonight. It just came down to a couple of pitches."

Nationals shortstop Ian Desmond was activated off the disabled list before the game and went 0-for-4. He had been out since July 21 with a torn left oblique muscle.

"Desi took some good swings tonight and looked great," Harper said. "To have our big guys come back and do well and get things going, it really helps."

The Nationals are 10-3 against New York so far this season.