A dejected Nationals dugout watches the winning streak end in the ninth inning. (John McDonnell/The Washington Post)

The stitches ran down the left side of Doug Fister’s neck. He insisted he never thought of them, or why they were required, as he fought Friday night to find his mechanics and preserve the Washington Nationals’ winning streak. He said it had no impact on his performance, however difficult that may be to believe.

After the 10-3 loss to the San Francisco Giants at Nationals Park, which halted the Nationals’ magical run at 10 games, Fister revealed the reason for the stitches. Between his last start, Fister underwent a minor operation to remove cancerous skin from his neck.

“I had some skin cancer removed a couple days ago,” Fister said. “It had no effect tonight.”

Fister did not say anything further about the procedure, other than that he is okay now. A Nationals media relations official cut short a group interview a second after he explained the stitches. Skin cancer is a scourge among baseball players, coaches and scouts who spend hours daily under the sun from spring training through the summer.

“Everything’s good with him,” Manager Matt Williams said, without revealing details. “He’s fine.”

So the Nationals had something larger on their minds than the end of the longest winning streak in team history, which doubled as the longest in the majors this season. Their magic carpet ride stopped Friday with an ugly finish. Old nemesis Tim Hudson held the Nationals down, and the Giants piled on six runs in the final two innings on the rare night Fister lacked sharpness.

“We haven’t had that feeling in a while,” first baseman Adam LaRoche said. “Tough loss, just the way we got beat. Other than that, looking back, it was an awesome stretch. Frustrating, but we’re still in great position for this time of the year. We just kind of let one get away from us today.”

The Nationals had won 14 of Fister’s past 17 starts, and he carried a 2.20 ERA into Friday night. He had not allowed more than three earned runs or multiple home runs in a start since June 15. But the Giants scored four runs off him in six innings that took him an uncharacteristically arduous 107 pitches to complete. Rookie Joe Panik blasted a three-run homer in the fourth, the first homer of his career, for one of his four hits. Buster Posey added a solo blast in the sixth.

“The whole day, I battled myself,” Fister said. “That’s a constant challenge for me, to constantly keep the ball down. It’s something I have to do. If not, I have to pay for it. And that’s what happened.”

The standard Fister set for himself since he debuted May 9 made his outing seem poor, almost shockingly so. But he still gave the Nationals a prime chance to win, his manager and teammates believed.

“It’s not a bad start,” Williams said. “They took two really good swings, and that gave them their four runs. Nobody is going to be good every single time.”

“You haven’t seen that happen all year,” center fielder Denard Span said. “It’s going to happen. That’s a good lineup over there. He still pitched good, in my opinion. He still gave us a chance to win.”

Since the All-Star Break, Rafael Soriano has three blown saves and a 7.71 ERA in 11 appearances. The Post Sports Live crew debates whether the Nationals should be concerned by the closer's performances. (Post Sports Live/The Washington Post)

Another walk-off, potentially the Nationals’ sixth in seven games, still seemed plausible until the eighth, when the Nationals trailed, 4-2.

Williams stuck with left-hander Jerry Blevins after he got out five of the first six batters he faced. But Blevins allowed a two-out rally in the eighth inning, which culminated with Travis Ishikawa’s two-run double off the right field wall.

“Things kind of unraveled there,” Williams said. “But he’s facing all lefties, and we feel confident in him to do that. It didn’t work tonight.”

The Giants tacked on another four runs in the ninth off Ross Detwiler and the shabby defense behind him. The mess ensured there would be no walk-off, no Gatorade buckets dumped on teammates, no smoke machine in the clubhouse.

In a quiet locker room, the Nationals did not spend much time on reflection. “We don’t have time to do that,” Fister said. “We got to come back tomorrow ready to play.” But they could still appreciate the run they made.

“Some guys were talking about it after the game,” LaRoche said. “Let’s start up a new one.”

The Nationals succumbed to Hudson — again. In 30 career starts against the Nationals, most of them with the Braves, Hudson had pitched to a 2.37 ERA. In June at AT&T Park, he allowed them no earned runs over seven innings. Friday, he held the Nationals to two runs, one earned, in 51 / 3 innings.

The Nationals scored first when LaRoche followed Anthony Rendon’s lead and executed a double steal in the first inning. Posey’s throw got away from Panik, and Rendon scooted home to give the Nationals a 1-0 lead.

Aided by Asdrubal Cabrera’s twisting, jumping play in the second inning, Fister cruised into the fourth, still holding the lead. After two quick outs, Pablo Sandoval hit a nubber just over Fister’s outstretched glove, which is no small feat (Fister is 6 feet 8). The infield single kept the inning alive for Michael Morse, whose grounder skipped past Ian Desmond’s dive and into center field.

Needing to retire the rookie Panik, Fister made a rare mistake. He left a first-pitch sinker thigh-high and over the middle of the plate. Panik smashed it over the center field fence, just to the right of the 402-foot sign. Fister had not allowed three runs in a start since July 2 in Colorado. With one swing, he trailed, 3-1.

“I just wasn’t sharp,” Fister said. “I left too many balls over the plate.”

Jayson Werth responded in the bottom of the inning. He had battled inflammation in his right shoulder, which required a cortisone shot and sapped his power. But he hooked Hudson’s 1-2 splitter into the left field seats for his first homer since the all-star break and slashed the deficit in half.

“They battle and they play hard,” Williams said. “We’ll see if we can start another one tomorrow. Those don’t come around very often. It’s pretty rare to see 10 in a row. We got to get back to work.”