Nationals reliever Ross Detwiler sits in the dugout after giving up a two-run homer in the 15th inning. (Toni L. Sandys/The Washington Post)

Three hitters stood between Aroldis Chapman and the end of the night, and that almost always means the end of the night is near. His jet-fueled left arm can turn any trio into fodder, and the Washington Nationals’ lineup fed him Danny Espinosa, Kevin Frandsen and Scott Hairston: one batter mired in a vicious slump and two charged with watching for three hours before facing a triple-digit fastball. You think your job is hard?

The end of the night, they made sure, would not come for a long while. Their heroics allowed the Nationals to twice come within a couple blades of grass of a victory and led, ultimately, to anguish. The Cincinnati Reds snatched away a Nationals walk-off in extra innings with preposterous diving catches in the 12th and 14th, staying alive until Ross Detwiler sealed the Nationals’ 4-3, 15-inning loss by allowing Todd Frazier a two-run homer mashed into the red seats.

Nationals players gathered in their clubhouse, laying on the floor and huddling in chairs, still hashing out the details. “It sucks to lose,” Frandsen said. “It lights something under you. But it was a great game. You can't get down on that.” They would need to swallow hard and come back Tuesday to face Johnny Cueto, only the best pitcher in baseball so far this year.

“You have to just understand that it's one game,” Manager Matt Williams said. “Just because you play more innings than normal doesn’t make it more gratifying to win or less gratifying to lose. A loss is a loss, and a win is a win.”

The marathon game materialized against Chapman in the ninth, when Espinosa snapped his skid and Frandsen and Hairston each supplied meaning to the cliché “professional at-bat.” Espinosa doubled, Frandsen and Hairston each whacked flyballs deep enough to advance him one base, and the top step of the Nationals dugout filled with applauding teammates.

So many any of them had helped push the game past midnight, keeping the game alive for 4 hours, 58 minutes. There was Stephen Strasburg, who squared off against childhood teammate and adult nemesis Mike Leake for seven two-run innings. There was Ryan Mattheus, who tossed two scoreless relief innings one day after taking a 7:30 a.m. flight from Class AAA Syracuse. There was Anthony Rendon, whose diving stop along the third base line would save a run — and bail out Rafael Soriano — in the top of the 10th.

The Nationals needed seven scoreless innings from their bullpen, which lowered its collective ERA to 1.97, best in the major leagues, before Detwiler took the mound. They needed Drew Storen to collect himself for a critical strikeout after a lengthy challenge delay in the 11th. They needed Aaron Barrett to squirm out of a two-on, no-outs jam in the 13th, and then pitch the 14th. They needed Denard Span’s RBI single in the seventh.

But they could not overcome Reds second baseman Brandon Phillips’s breathtaking, game-saving, diving catch with two outs in the 12th. And they were collapsing in the home dugout after center fielder Billy Hamilton sprinted into right-center and robbed Rendon of a walk-off single in the 14th.

The Nationals’ bullpen piled up scoreless innings until Williams called on Detwiler, who last pitched Friday, in the 15th. When he took the mound, the Nationals had thrown 272 / 3 consecutive scoreless relief innings. Phillips led off with a single under Espinosa's dive. Two batters later, Frazier launched a 2-1 change-up over the left-center field fence.

“I'm trying to get a groundball right there," Detwiler said. “Bad execution. Bad pitch selection. It was bad all the way around. It was just one bad pitch. It was stupid. It sucks that our team is out there fighting all night long, and I make one mistake and that pretty much cost us the game.”

The Nationals had missed a golden chance in the 14th. Frandsen led off with a double to the left field corner against right-hander Logan Ondrusek. Williams had a choice: use backup catcher Jose Lobaton, his last pinch hitter, and let him try to win the game with a hit, or use a pitcher — likely Tanner Roark — to bunt Frandsen to third. Williams chose Lobaton.

"We've got one guy left on the bench, and we've got to take our shot to win the game," Williams said. "We can try to bunt him to third with a pitcher, but Lobie's on the bench. We got to take our shot. He looked to get a ball over to the right side."

But he could not — Lobaton he struck out. Span made an out, and the inning fell to Rendon. He stung a liner to center, and players in the dugout rushed to hop over the rail.

“I hit it good. I knew it,” Rendon said. “I knew he had a chance to catch it. I was hoping it might die. It didn't die.”

Hamilton robbed him, sliding on his stomach. Hamilton is the fastest player in baseball. If he had been the second-fastest, the Nationals would have celebrated. Instead, Gio Gonzalez crumpled on Jordan Zimmermann's shoulder in the dugout.

“Everyone in the stadium thought that was going to get down,” Frandsen said. 

Jayson Werth led off the bottom of the 15th with a double, and he scored on Greg Dobbs's two-out bloop single to right. Espinosa rocked a fastball to the warning track in right field, only adding one final dollop of anguish.

The pain could have been averted if not for the ninth. With a lineup diminished by injuries, the Nationals accept many of their wins this month must be grinded out. Their ninth-inning scrap against Chapman symbolized that ethic.

Espinosa walked to the plate with six hits in 53 May at-bats. Williams said he needed to narrow his pitch selection and stop trying to "hit everything." Slump or not, Espinosa can handle elite velocity, as long as he waits for a strike to hit.

Against Chapman, Espinosa fouled off a fastball for strike one, then refused to chase three consecutive pitches outside the strike zone. Chapman blazed a 99-mph fastball at the knees, and Espinosa laced it into the left field corner for a double. Instantly, the tying run stood in scoring position.

Williams pulled Nate McLouth for Frandsen, the do-everything reserve with the perma-dirty uniform. Chapman fired a neck-high, 100-mph fastball, and Frandsen swung through it. On the next pitch, Frandsen bashed another 100-mph fastball deep to left-center field. Espinosa tagged and scooted to third. Frandsen pumped his fist and accepted high-fives from every teammate in the dugout.

“You know coming into the series, you're going to face Chapman,” Frandsen said. “I don't put a lot of pressure in those situations, because he's going to provide a lot of stuff. My whole goal there was take a chance on the first one, and then after that, make sure he moved over.”

Hairston's turn. Down to his last strike, Hairston bashed a 1-2, 100-mph heater to the edge of the warning track in left field. The park erupted as soon as he made contact. Espinosa cruised home and tied the game at 2.

Storen survived a spotty and lengthy 11th. Frazier led off with a single, and Heisey's one-out walk put two runners on base. Rendon snagged Zack Cozart's liner to third and caught Heisey creeping off first base. He rifled a throw across the diamond. Greg Dobbs, playing in the field for the first time since last summer, stretched. The throw beat Heisey, but did Dobbs's foot stay on the base?

Umpires called him safe, and Williams challenged the ruling. Storen fired warmup pitches as the umpires took 3 minutes 39 seconds to determine the replay inconclusive. Once play resumed, Wilson Ramos let the first pitch deflect off his mitt and trickle to the backstop, putting both runners in scoring position.

With the count 2-2 on Ryan Ludwick, Ramos called for a change-up. Storen nodded. He threw it high, and it dropped into the strike zone. Ludwick froze. Storen escaped. 

Tyler Clippard, Storen's change-up-chucking best friend, handled a 1-2-3 12th, and Tyler Moore led off the bottom of the inning with an eight-pitch walk off J.J. Hoover. With two outs and Span on third, Ramos hit a soft liner up the middle. The Nationals readied for a celebration. Phillips laid out and snared the ball behind second base.

The Reds held the momentum into the top of the 13th, putting their first two runners on against Barrett. In five pitches, Barrett escaped — Neftali Soto botched a sac bunt, and Heisey grounded into a 5-4-3 double play.

Strasburg yielded two runs, six hits and a walk in seven innings, striking out four. Both runners who scored reached when Strasburg hit them with a mid-90s sinker that tailed too far inside. Otherwise, he danced around base runners and kept the Nationals close for 96 pitches.

“I battled,” Strasburg said. “Fastball was up a little bit tonight, but I tried to keep it close.”

Hamilton, a force unlike any other in baseball, nearly stole another run – and perhaps he would have if the umpire had made a different call. In the seventh, Hamilton advanced to third with two outs. Strasburg toed the rubber from the wind-up, akin to leaving a door unlocked for a thief. As Strasburg started his wind-up, the fastest player in baseball bolted for home.

Strasburg hurried his delivery and threw a strike to Wilson Ramos. As the Nationals engaged in a rundown, Cincinnati players moved to the top step of their dugout and pointed at the plate. They wanted a balk called on Strasburg. The rule states a pitcher cannot alter his delivery, and Strasburg had sped up. But the umpire ruled in the Nationals' favor, and the inning ended.

“I thought about — I was either going to go out of the stretch or out of the wind-up," Strasburg said. “I said, ‘If he decides to break, then I can just throw it home anytime out of the wind-up.’ I just wanted to make sure my stuff was there for Phillips. He's a good hitter and knows how to get his RBI. He just helped me out by taking the bat out of his hand.”​