Andrew Toles scores the go-ahead run for the Dodgers in the eighth inning of Game 4. (Jonathan Newton/The Washington Post)

The constant for these Washington Nationals, through their postseason ups and downs and the steady regular seasons that got them there, is starting pitching. They draft it and they stockpile it, they protect it and they spend for it, because without it, things eventually fall apart.

The wear and tear of four short outings undid the Nationals in their 6-5 loss to the Los Angeles Dodgers in Game 4 of the National League Division Series on Tuesday. Their stunning three-run comeback went for naught because a tired bullpen couldn’t hold this time. Joe Ross did not last three innings. Nationals starters are averaging four.

“It puts a lot of pressure on you to try to figure out who is the strongest, who is the most rested,” Nationals Manager Dusty Baker said. “You try to do the matchups the best you can.”

No one moment spoiled the Nationals’ bid to clinch their first NL Championship Series appearance, no one mistake forced them to play a Game 5 on Thursday night. Chase Utley’s go-ahead single off Blake Treinen in the eighth was hardly a mighty blow.

“Our guys have done a phenomenal job. It’s just unfortunate. They made some good swings today,” said Treinen, who thought the slider Utley grounded hard to the right of second was a decent pitch. “. . . Unfortunately, I was the one on the mound when it happened and they were able to beat me today.”

The Nationals’ bullpen had allowed one run in 16⅔ innings when a walk and a seeing-eye single put Treinen in trouble. Their relievers have allowed two runs in 17⅔ innings entering Game 5 — a 1.02 ERA. Their starters — who combined for the second-lowest ERA in baseball during the regular season — have allowed 13 runs in 16⅓ innings — a 7.16 ERA.

Yet the Nationals almost won the series in four games anyway, undeterred by those uncharacteristic showings — most recently the four runs Ross allowed in 2⅔ innings. When they fell behind three runs to Clayton Kershaw, and were still three back with two outs in the seventh, they rallied.

“Man, that’s what baseball is all about right there,” Baker said. “A matter of will.”

It began in the unlikeliest of places, against the ace of all aces, tired though he was. It began with Danny Espinosa, the beleaguered shortstop who had been hit by the ball more often than he had hit it this series, greeting Kershaw — who was approaching 100 pitches — with a single to left field to lead off the seventh.

By then, Espinosa had struck out nine times in 10 postseason at-bats and was hit by pitches in three other plate appearances. After striking out twice more against Kershaw on Tuesday, Espinosa adjusted, with the kind of opposite-field single his manager and others have implored him to seek.

“I just told myself to spread myself out a little more and just be on time,” Espinosa said. “. . . He was pounding me in, pounding me in, and I just needed to simplify right there to make my swing be on time.”

The Post's Jorge Castillo and Chelsea Janes preview the NLDS between the Nationals and Dodgers. (Jayne Orenstein/The Washington Post)

Espinosa beat out a two-out throw to second base on a force play that put two men on for Bryce Harper. Harper fell behind Kershaw 1-2 before taking a few close pitches in a gutsy walk. Kershaw left after that, and the Dodgers’ bullpen — also exhausted — let the Nationals tie it.

With two outs and the bases loaded, Daniel Murphy drove a single to left-center to tie the game. He drove in four of the Nationals’ five runs, a new franchise record, and is hitting .462 in the series. But Anthony Rendon struck out, which left Jayson Werth stranded on third, so the Nationals did not take the lead. An inning later, the Dodgers did.

Until that point, Oliver Perez, Reynaldo Lopez and Marc Rzepczynski had combined to hold the Dodgers to one run. Lopez was the Nationals’ other choice to start Tuesday, but because he had proved himself out of the bullpen and Ross had not, the Nationals chose Ross — confident that Lopez could go several innings if Ross did not last.

Perez was first to relieve Ross, but Lopez took over for the fifth inning, at which point the Nationals trailed. He threw two innings and struck out three but had to be lifted for a pinch hitter in that seventh-inning rally — which forced Baker to go to Rzepczynski then Treinen, the only relievers he had left who had not been used to their short-term limit in Monday’s win.

“When you look at it, maybe it’s just their day,” Baker said. “. . . You’ve got to pick your poison. Didn’t work.”

Such are the choices Baker has faced over and over again this series, because his starters have forced him to his bullpen early and his bullpen has had to pitch strenuous innings late. The Nationals did not collapse Tuesday — in fact, they fought back — but they lost anyway. They will have a day off to rest their bullpen for Game 5, when Max Scherzer will be on full rest, as likely a candidate as any to give these Nationals the kind of start that got them here in the first place.