WASHINGTON -- Washington manager Dusty Baker was in the Nationals' dugout in the top of the 18th inning when he looked over and saw Jonathan Niese, a reliever for the Pirates, standings in the on-deck circle with two outs and Starling Marte at the plate.

With the game tied at 1-1, Baker realized that Niese was going to bat for himself against Washington reliever Oliver Perez.

But before Baker could alert Washington catcher Wilson Ramos about Niese, Marte slammed the first pitch from Perez into the left field bleachers for a solo homer and the Pirates held off a rally in the last of the 18th to beat the Nationals 2-1.

"That was my fault. It falls on me," Baker said.

Marte, Adam Frazier and Jordy Mercer had three hits for the Pirates, who won despite leaving 12 runners on base in a game that saw 540 pitches.

Former starter Niese (8-6), who was recently sent to the bullpen, threw three scoreless innings to get the win while Perez (2-3) gave up two hits and the one run in two innings.

"It is my job to know the situation," Perez said through a translator, when told that Baker owned up to the miscue. "It was my mistake."

It was the longest regular-season game in terms of innings in Nationals' franchise history. Niese struck out Danny Espinosa with two runners on base in the bottom of the 18th to end the game.

"I believe this is great motivation for the rest of the season," Marte said through a translator. "It shows that we're together, we're here to fight, we're here to fight for a win, and that's just who we are. Too many innings, we were tired, it was time for a home run."

The Pirates had a chance to take the lead in the top of the 16th when Josh Harrison hit a two-out double to center. But reserve catcher Eric Fryer, who had walked with two outs, was thrown out at the plate on a strong relay from shortstop Danny Espinosa to catcher Wilson Ramos to end the frame.

The Nationals won a 16-inning game at home over the Minnesota Twins on April 24 when Chris Heisey hit a walk-off homer. That same day the Pirates won a 13-inning game at Arizona, which had been their longest game by innings this season until Sunday.

"A relatively fast 18-inning game. I don't know if that is possible," Pirates closer Mark Melancon said.

Pittsburgh was one strike away from winning by a 1-0 score when Daniel Murphy, the leading hitter in the National League, hit a solo homer with two outs in the ninth on a 2-2 pitch from Melancon in a battle of NL All-Stars. Murphy did not start due to a sore hamstring.

"I just tried to get a good pitch to hit," Murphy said. "Mark is so tough. I just saw him at the All-Star game. He was very deserving to be there."

Washington had a chance to win the game in the 14th but Jayson Werth, who had two walk-off RBIs in June, flied out with speedy Trea Turner (two hits) on second base to end the threat. Turner singled to lead off the 17th but was thrown out at second by Marte.

Marte lined a fastball off Washington starter Max Scherzer for an RBI double and a 1-0 Pittsburgh lead in the sixth. His hit with one out scored Frazier, who led off with his second double of the game.

Pirates starter Chad Kuhl was making his fourth major league start and making his big league debut June 26 against the Angeles Dodgers. He struck out five with no walks while throwing 85 pitches Sunday, 54 for strikes.

The right-hander gave up a single to Ben Revere with one out in the first and then retired the next 14 batters before Espinosa was hit by a pitch to lead off the sixth.

Kuhl had allowed 18 hits in his first 13 1/3 innings in the majors and entered the game with a 6.08 ERA. Scherzer allowed one run on six hits with seven strikeouts in seven innings. Scherzer threw a no-hitter at home against the Pirates on June 20, 2015.

"A lot of good came out of today," Scherzer said of his outing.

Washington (56-37) had won five in a row while the Pirates (47-45) had lost three in a row.

"I just love the grit of our club," Pittsburgh manager Clint Hurdle said. "I don't know if (a game like this) builds character, but it definitely reveals character. You've got to keep playing."

NOTES: The Nationals entered Sunday's game leading the National League in home runs (126), team ERA (3.23) and fielding percentage (.990). They have a league-low 33 errors. ... Pirates RHP Chad Kuhl was expected to have at least 20 family members and friends on hand for the game. He is a product of the University of Delaware and is from Bear, Del., which is less than two hours north of Nationals Park. Kuhl is the fourth Pittsburgh pitcher to make his major league debut this year as a starter. ... Washington 2B Daniel Murphy, the leading hitter in the league at .348, was out of the starting lineup for the third day in a row with a hamstring injury. Trea Turner started at second base. ... Nationals 3B Anthony Rendon was not in the starting lineup due to the flu. INF Stephen Drew, who had three doubles Saturday, started at third for Washington.