Jayson Werth chalks up another 0-for-4 on Tuesday to drop his average to an anemic .221. (Carolyn Kaster/Associated Press)

The Washington Nationals have existed this season in a state of perpetual tension, and Tuesday night, even after they momentarily pummeled a 38-year-old who pitched in Japan three years ago, they found themselves facing another pivotal moment.

A three-run lead had turned to one. Ross Detwiler had left his stellar first start this season on a sour note. Their offense had again gone missing. The tying run stood on second base. The Chicago Cubs’ leadoff hitter stood at the plate.

In their most tense moments they have turned to the same Rec Specs-wearing, funky-throwing all-star. Tyler Clippard came in to put out another fire, and his latest tour de force from the bullpen preserved a 3-2 victory over the Cubs for the Nationals and Detwiler, who allowed two runs in 5 1/3 innings in his first major league start this season. Clippard stranded the tying run at second base in the seventh inning and retired all four batters he faced, striking out two of them.

Before 19,181 at Nationals Park, the Nationals won for the 12th time in their last 15 one-run games. The latest ended only after Danny Espinosa made a running, bare-handed stop and a bullet throw to Alex Cora, whose drop at first one batter earlier had squandered a potential game-ending double play.

“These games, oof,” Manager Davey Johnson said. “My goodness.”

Now 44-43, the Nationals surged back over .500 despite a continued dearth of offense. They touched Ramon Ortiz for three runs, two earned, in the first inning, but he struck out seven and allowed no extra-base hits in six innings. Jayson Werth went 0 for 4 with two strikeouts and a double play, dropping his average to .221 this season. “I think he’s bottomed out,” Johnson said.

They’re winning, anyway, with improbabilities tumbling atop improbabilities. In their past 11 victories, 11 different pitchers have earned a win. Their last nine victories have all come either by one run or in extra innings. Since June 1, they’ve won 10 games while scoring three runs or less.

“It’s not letting the pressure get to you,” said closer Drew Storen, who secured his 21st save. “It comes down to just trusting yourself in those situations. Those are tough games. If we want to get to where we need to be, we need to play those games.”

No one has thrived on it more than Clippard. He entered in the seventh with Tony Campana on second base and the Nationals up a run. Reed Johnson, who had smacked two balls to the warning track, stood at the plate. Clippard threw him a slider for a ball, a rare departure from his change-up-fastball guessing game. Then he fired three straight fastballs. Johnson swung and missed all of them, the last one 93 mph.

Clippard then pitched a perfect eighth, giving him perhaps the game’s most crucial four outs. The Nationals have consistently given Clippard the most difficult assignments – “I watched two or three where Houdini couldn’t get out of those jams,” Johnson said – and he has stranded 26 of 32 base runners. He struck out two of the four batters he faced, upping his strikeout total to 61 in 48 1/3 innings while lowering his ERA to 1.86.

“There’s a comfort level there,” Clippard said. “The confidence is there. It definitely plays a part, for sure.”

Storen earned the save, with help from Espinosa. With two outs in the ninth, speedy rookie Darwin Barney chopped a high bouncer to second. Espinosa avoided the runner and grabbed the ball with his bare hand. “That was the only shot,” Espinosa said. “If I would have gloved it, it would have taken too long.”

In one motion, Espinosa snared the ball and fired a bullet to first. The Nationals sprang out of the dugout to celebrate another nip-and-tuck win.

“I didn’t really think there was any way,” Storen said. “That’s an unbelievable play.”

Detwiler climbed the Nationals Park mound Tuesday night for the first time since last September. The Cubs ripped a several line-drive outs straight at fielders, but Detwiler cruised through his first five innings despite only one strikeout. He walked no one and allowed two hits, both singles, entering the sixth inning.

Through his career, the primary knock against Detwiler has been his inability to maintain his best stuff though late into the game. The first batter Detwiler faced in the sixth inning, Johnson, was also the first batter he saw for the third time. Johnson smoked a double to left. After Blake DeWitt hit a sharp lineout to center, Aramis Ramirez came to the plate.

Detwiler fell behind, 1-0, with a sinker, his best pitch all night. He threw a change-up off the outside edge of the plate, a well-placed pitch. Ramirez lunged across the plate and hooked it high in the air to left. Detwiler turned and watched.

“I thought it was going to be caught,” he said. “The ball just kept going.”

He stared, stunned, as the ball landed about six rows deep. Johnson trudged to the mound and replaced him, regretting having not brought in Todd Coffey to face Ramirez, a right-handed hitter. “I’m rusty,” he said. “I messed that up.”

The Nationals’ offense had provided another thin margin for error. They have not scored more than five runs in a nine-inning game since June 21, but they gave themselves a chance to break out.

Roger Bernadina, Espinosa and Ryan Zimmerman greeted Ortiz with three consecutive singles, loading the bases with no outs. Cleanup hitter Laynce Nix gave the Cubs an opportunity to get off easy, rolling a groundball to the right side. Jeff Baker fielded it, turned to second and rifled a throw in the general direction of second base, about 20 feet off target. It rolled into the outfield, allowing two runs to cross.

Wilson Ramos drove in another run with an infield single off third baseman Aramis Ramirez’s glove, making in 3-0 in the first. The Nationals managed little against him the rest of the night, which only allowed them to win another nail-biter.

“We’re winning games when we’re not hitting on all cylinders,” Johnson said. “It makes it interesting.”