Twenty minutes after midnight Monday morning, after watching the New York Mets complete a three-game sweep of his Washington Nationals, Manager Dave Martinez didn’t express frustration. There was no angst. He insisted the club has played good baseball. One hit here, one hit there, he said, and the Nationals aren’t 4-5 in the midst of a five-game losing streak. He maintained his team is playing well and will turn it around. The odds are on his side. The regular season is less than 10 percent complete. Alarms don’t sound this early for a club expected to contend for a World Series.

Still, these are the facts following the Nationals’ 6-5, 12-inning loss to the Mets on Sunday night: They are under .500 for the first time since August 2015, their five-game losing streak is longer than any they endured last season, and they have already matched the number of times they were swept at Nationals Park in 2017 after one home series.

Those facts exist because Tanner Roark encountered strange two-out troubles, because the Nationals were sloppy on the base paths and because they twice wasted opportunities with the bases loaded on Sunday. They left 13 runners on base. They squandered another monster performance at the plate by Bryce Harper and the six scoreless innings from their bullpen were reduced to a footnote after Brandon Kintzler’s latest troubles in the 12th.

For the third straight game, the Nationals turned to Kintzler, and for the third straight game the right-hander stumbled, surrendering a game-winning, broken-bat RBI single to Yoenis Cespedes. Kintzler allowed seven runs in three innings in the three-game series. His ERA stands at 15.75. But he said Sunday was different. Unlike the previous two outings, he believed he pitched well. He said he was mechanically sound and he executed his pitches. He pointed to the two bats he broke and the groundball he produced. And he knows that isn’t enough.

“When it’s bad it’s bad,” Kintzler said. “And it’s going bad…There’s nothing else I could’ve done. Maybe could’ve hit him.”

The Nationals opened the scoring for the third straight day because Harper unleashed another power display. After Anthony Rendon singled, Harper demolished a low fastball from Matt Harvey through the frigid air to give Washington a 2-0 lead in the first inning. The home run was his league-leading sixth. Five teams have hit fewer.

Roark’s stuff looked crisp for much of his outing. He was swinging his two-seam fastball back over the plate. He was inducing swing-and-misses with his curveball. He resembled 2016 Tanner Roark more than 2017 Tanner Roark. But, strangely, a switch flipped with two outs, and he paid a steep price. After getting two quick outs to begin the third, he issued a 3-2 walk to Jay Bruce. Then he issued a 3-2 walk to Todd Frazier. Then he issued a 3-2 walk to Asdrubal Cabrera, just missing with a fastball inside to grant the free pass.

“I was just missing by just that inch or so,” Roark said.

Suddenly, the bases were loaded and Roark was laboring. His pitch count read 65. With Adrian Gonzalez coming up, Nationals pitching coach Derek Lilliquist used the first of Washington’s six mound visits. Lilliquist cautioned Roark that Gonzalez would come up swinging, and he was right. Roark threw a four-seam fastball to begin the at-bat and veteran first baseman was waiting for it. He pounced on the 89-mph offering, smashing it into Washington’s bullpen over the right field wall. The grand slam pushed New York ahead 4-2. Again, the Nationals jumped out to a lead against their rivals. Again, they squandered it.

The two-out pattern continued in the fifth when Cabrera smacked a two-out solo home run on Roark’s 99th pitch. Roark threw one more to get the elusive third out and end his night without any more damage. The Mets (7-1) finished 5 for 10 with two home runs, two doubles, four walks and five runs with two outs against Roark. They went 0 for 10 with six strikeouts with no outs or one out.

“I think he just started cutting corners a little bit,” Martinez said. “When that happens, you get to two outs, last thing you want to do is walk somebody.”

Trailing 5-3, the Nationals halved their deficit in the bottom of the inning when Trea Turner drove home Harper, who had collected his third hit to lead off the frame. Washington was threatening to score again after Turner swiped second base and Michael A. Taylor hit a squibber in no-man’s land between Harvey and Gonzalez to reach. Turner, however, rounded third base too aggressively, disregarding third base coach Bob Henley’s signal to stop on the bag, and Gonzalez threw across the diamond to trap him in a rundown. Instead of having runners on the corners for the hot-hitting Pedro Severino, who had doubled in his previous plate appearance, Turner was tagged out to conclude the inning.

“I thought there was going to be a play at first,” Turner said. “With the pitcher coming and the flip, I thought it would be a good time to be aggressive, and the flip just never happened.”

The score held until Taylor’s RBI single in the seventh inning off Robert Gsellman tied the game. Then, in the eighth, the Nationals were lurking again after Rendon worked a two-out walk to bring up Harper. The Mets countered with Jerry Blevins, a left-hander, to maximize their chances of finally retiring Harper, who stepped into the batter’s box 3 for 3 with a walk. But Blevins didn’t need to get Harper out to do his job. Instead, he picked off Rendon.

In the ninth, Seth Lugo walked Harper on five pitches and kept his focus on him as he creeped off first base, which prompted a bad throw over to the bag. Harper scurried to second base and Henley was waving him over to third. But Harper stayed put. A couple of pitches later, Matt Adams lofted a flyball far enough for Harper to tag up on. It would’ve won the game if Harper was at third base.

“I just didn’t want to get thrown out at third,” Harper said. “No outs, in that situation, you’re in scoring position from second base. Could I have gone? Possibly, but for me I just didn’t want to get thrown out.”

With Harper on third and one out, the Mets elected to intentionally walk the next two batters to load the bases. Lugo then struck out Taylor on three pitches. Then he did the same with Severino.

Three innings later, after a two-inning scoreless effort from Sammy Solis, Kintzler stumbled again. First, pinch hitter Juan Lagares singled. Amed Rosario then moved him to second base with a sacrifice bunt. With first base open, the Nationals, playing the matchup and a double play, decided to intentionally walk the left-handed Michael Conforto to get to Cespedes. The strategy backfired. Cespedes muscled a 94-mph sinker in on the hands to shallow left field to score Lagares.

The Mets dugout - and the contingent of blue-and-orange-clad fans behind it - erupted, the outburst echoing in the empty ballpark just before the clock struck midnight.

“Hopefully in September we’ll just be laughing about this,” Kintzler said. “We just need one win to get us going.”