Tanner Roark allowed three hits in seven innings against the Marlins but lost, 1-0. (Alan Diaz/Associated Press)

As the home run that ultimately decided a 1-0 loss to the Miami Marlins flew over Bryce Harper’s head and then over the right field wall, Tanner Roark turned to home plate umpire Phil Cuzzi, who had wandered up the first base line. Roark did not yell, or slump his shoulders. He held up his glove to Cuzzi, who was confused for a moment, because recently beaten pitchers do not generally ask for the ball so quickly.

That moment, as much as any, sums up the Washington Nationals right-hander, who is perpetually undaunted — and who nearly sealed his status as one of baseball’s elite starters by outdueling another, Jose Fernandez, with seven innings of one-run ball Tuesday night.

Were it not for that home run, an 0-1 fastball driven the opposite way by Giancarlo Stanton, Roark might have matched Fernandez. Needing perfection against the long-standing nemesis of a scuffling Nationals offense, Roark could not deliver it and the Nationals lost their fourth straight game.

“We’re all frustrated, especially when you’re not scoring runs,” said Nationals Manager Dusty Baker, whose team has scored more than three runs just twice in nine games. “It was tough to take because Tanner pitched better than a loss tonight.”

If there were any doubt that Roark, with his 15 wins and top-five ERA, could be a reliable No. 2 starter if Stephen Strasburg cannot pitch in October, he has done all he could to mollify it. He has now thrown 200 innings for the first time. He still leads the league with nine starts of seven or more scoreless innings.

“It’s good and all, but we lost so I’m pretty mad about that,” said Roark, whose voice betrayed the frustration. “The only thing that matters is winning and losing. Tonight we lost.”

None of his pitches stand out as particularly stupefying, as, say, Fernandez’s 99-mph fastball, but he commands them all and throws them with uncommon fearlessness. His success is not the product of an average pitcher pitching almost perfectly but of a good pitcher pitching without fear of imperfection.

“He’s very good. Works corners, in and out,” said Stephen Drew, who had two of the Nationals’ four hits Tuesday. “Keeps hitters off balance, and I think he comes at you at the same time.”

Roark said he thought the pitch to Stanton was a good one — a fastball, low and away, though it might have come back over the plate a bit. He finished the sixth inning, then worked a scoreless seventh, after which he headed into the dugout yelling at his teammates — fired up, not taking shots — urging them to rally against Fernandez.

They did, as hits from Wilson Ramos and Brian Goodwin gave them runners on first and third with one out in the eighth. Because they rallied, Roark’s night ended after seven innings. Danny Espinosa struck out for the second out. Baker pinch-hit Daniel Murphy, whom he had saved for a two-out situation so Murphy would not have to run as much on his sore left leg, with two outs in the eighth. Murphy grounded out.

Roark allowed three hits — same as Fernandez. He did not have spotless command of his fastball Tuesday, but he has lifted himself into the tier of elite starters by working around trouble like that.

With two outs in the third inning, he allowed a groundball single to Marlins leadoff man Dee Gordon. He then walked Marcell Ozuna on four pitches and Martin Prado on five, an uncharacteristic lapse in fastball command that meant many of his pitches missed the plate wide. In a bases-loaded jam of his own making, Roark challenged Marlins cleanup man Christian Yelich with a fastball. Yelich lined it to shortstop to end the inning.

“I wasn’t being as aggressive as I wanted to be,” said Roark, who finished his seven innings with 86 pitches despite three walks — one of his more efficient outings of the season.

He finished the night with his 12th start of seven innings or more and one run (or fewer) allowed, tied with the Chicago Cubs’ Jon Lester for the most in baseball. Normally Roark has more margin for error than he did Tuesday, because the Nationals hit every starter in baseball better than they hit Fernandez.

The young right-hander, second only to Max Scherzer in strikeouts, finished the evening with a 0.99 ERA and 8-0 record against the Nationals in his career. Drew’s first-inning double was the only hit the Nationals would get against Fernandez until that eighth-inning rally. Relying on his change-up to complement his high-90s fastball against the Nationals’ left-handed-heavy lineup, Fernandez allowed three hits in eight scoreless innings and struck out 12.

The recent sluggishness of the Nationals’ offense has slowed their chase of the National League East division title. As of game’s end, their magic number to clinch that title was five, and it moved to four when the New York Mets lost to the Atlanta Braves. The way Roark pitched, the Nationals only needed two runs to reduce it further. The way Fernandez pitches against them, they are usually happy to get one.

“The way I look at it is me versus him, not me versus the hitters or anything like that,” Roark said. “It’s me versus him, and tonight he got the win. They got the win.”