Washington starting pitcher Jason Marquis faced one significant disturbance against the Padres, when he loaded the bases in the fifth inning, but he navigated it for a 2-1 victory. (Denis Poroy/GETTY IMAGES)

Jason Marquis took a deep breath and stared in at the plate, his undemanding Friday night having turned into hard labor. The first 12 San Diego Padres he faced had not sent a ball into the outfield. Now, in the sixth inning, the bases were loaded, the Washington Nationals’ lead was slashed to one, a hotshot prospect dug in and the count ran full.

“You watch the way his demeanor didn’t change on the mound,” closer Drew Storen said. “We call them down in the bullpen, ‘Man-pitches.’ ”

In a bind he had not faced all night at Petco Park, Marquis turned to a pitch he had mostly kept holstered. In the pivotal moment of the Nationals’ 2-1 victory over the Padres, Marquis turned to a risky, perfectly executed change-up, beating a powerful rookie with veteran guile. By extricating himself from the only jam he faced all night — and on the back of Michael Morse’s two-run homer and dominant relief pitching by Tyler Clippard and Storen – Marquis secured his seventh win.

Following an early exit by ejection in his last start, Marquis gave up one run in six innings on three hits and three walks, striking out five. The Nationals improved their record on their West Coast road swing to 4-5, keeping alive the chance at their first winning, multi-city trip since May 2008.

Morse, Clippard and Storen chipped in, but they mainly had one pitch Marquis made to thank. When Rizzo walked to the plate with one out in the sixth inning, Marquis had just forced in a run by walking Ryan Ludwick with the bases loaded, cutting his lead to 2-1. Marquis had relied on his sinker and slider, throwing four change-ups all night. As he dueled with Rizzo and the count moved to 3-2, two of the five pitches he threw were change-ups.

“I wasn’t giving in in that situation with a pitch over the plate,” Marquis said. “If I had to face [Jorge] Cantu, the next hitter, with the bases loaded, tie ballgame, I’ll take my chances.”

Rizzo, after smashing a triple off the outfield fence Thursday night, was playing in the second game of his much-anticipated career. Marquis assumed a rookie in this situation would want to be aggressive. Marquis thought he needed to present a pitch as a strike, but have it fall out of the strike zone and make Rizzo chase it. He didn’t care that it was full count or that he had thrown just six out of 98 pitches. The change-up was the right pitch.

“I know what I’m capable of doing,” Marquis said. “I know what I want to do. I’m a big guy in the game will dictate in how I attack hitters. The game will dictate how you attack hitters, whether it’s how your ball is moving that day, the types of swings that hitters take off you. I felt like that was the right pitch at the moment.”

Marquis threw the change-up, starting it just above his kneecap. Just as Rizzo started a mighty hack, it dropped below his knee, almost to the dirt. Rizzo swung over it by about four inches, strike three.

“I don’t think he got me chasing,” Rizzo said. “That was just a great pitch. That change-up was in the strike zone, and then it dropped off. I don’t know of anybody who could’ve laid off.”

Marquis induced a grounder from Cantu and quelled the threat. “To come out of that with one run,” Manager Jim Riggleman said, “that’s good veteran pitching right there.”

Marquis had operated with a small margin for error. The Nationals’ offense did not snap its funk – it managed four hits and scored three runs or less for the seventh time in nine games. Their runs came from the most consistent – and, on some days, only – source providing it for them these days.

Morse came to the plate in the second, Laynce Nix on first after a single. Morse looked at two fastballs and quickly fell behind, 0-2. He took a ball, fouled off two pitches. Mat Latos threw him 92-mph fastball over the plate, and Morse unleashed his swing, which is becoming one of the most destructive swings in baseball. The ball rocketed into the night, into the upper portion of the second deck. Not many balls reach that part of Petco Park.

After he rounded first base, Morse tapped the top of his helmet with his left hand, a ritual that has become common. “I don’t even notice I do it,” Morse said. “Maybe I’m congratulating myself. Telling myself, ‘Good job.’ ”

Morse has been the Nationals best hitter at a time of the season when they have needed it most. Since May 22, the day after Adam LaRoche played his last game and he took over at first base, Morse has hit eight home runs, which ties him for second most in the major leagues over that span.

Once Marquis handed the ball to Clippard, “He just did what he always does,” Storen said. “He just dominates.”

Clippard faced seven Padres over two innings and allowed just a walk, striking out three helpless Padres. Clippard was both durable and dominant, combination that describes his entire season. Fifteen of Clippard’s 28 appearances have lasted more than three outs. He has struck out 46, second to Craig Kimbrel among major league relievers. Clippard has thrown 563 pitches this season, which ranks fourth in the majors.

For a while, it seemed like Marquis might not need any help from the bullpen. He allowed only base runner in the first four innings, a walk to Rizzo in the second. Cantu followed immediately by grounding up the middle, where Danny Espinosa had positioned himself perfectly and began a 4-6-3 double play. He struck out the side in the second, all three batters swinging at a sinker or slider and missing.

By the end of the fourth, Marquis had faced the minimum. Not only had he not allowed a hit. The Padres had not a ball out of the infield.

On the first pitch Marquis threw in the fifth, Ryan Ludwick ripped a double down the third base line, just past Alex Cora’s dive, to break up any no-hit chance. But after another zero, Marquis had run his scoreless streak to 112 / 3 innings.

The Padres stopped it there, and then they threatened for more. Marquis put himself into one of the toughest situations a pitcher can face, and then he made a pitch worthy of the jam. In the Nationals’ bullpen, that’s what they call a man pitch.