Journeyman Padres starter Eric Stults gets ready to deliver in the first inning against the Nationals. (Gregory Bull/AP)

The Washington Nationals’ lineup confronted a journeyman starting pitcher Saturday evening, and it still demanded near perfection out of Jordan Zimmermann. His offense allowed him no margin for mistakes, and in a crucial moment he made a decisive error on a simple play. Zimmermann remained unbeatable throwing the ball over the plate, until he turned and threw it to first.

After a 33-year-old lefty named Eric Stults shut down the Nationals for eight innings, their 2-1 loss to the San Diego Padres hinged on Zimmermann’s second mistake of the day. Trying to stifle a rally before it started, Zimmermann rifled a pickoff attempt into foul ground. The next batter, Everth Cabrera, cracked a go-ahead single into center field. It held as the game-winner after the ninth inning brought another fruitless frame for the Nationals’ sputtering hitters. It lasted 2 hours 1 minute, and everybody went home in time for dinner.

Zimmermann allowed two runs, one earned, on seven hits and no walks in an 85-pitch, eight-inning complete game, lowering his ERA to 1.62. He still could not become the first major leaguer to reach eight wins. Zimmermann also singled, one of the meager four hits, all singles, the Nationals managed.

“He pitched an unbelievable game and swung the bat better than most of the guys in the lineup,” Manager Davey Johnson said. “It’s a waste we couldn’t pull this one out. That’s a tough loss.”

The Nationals had scored six runs in each of the past two games, powered by a surging middle of the order. Their offense, dreadful all season, threatened respectability. But with Bryce Harper sidelined with a swollen left knee and their sluggers silenced, the Nationals had almost no other offense to speak of.

They have a second baseman, Danny Espinosa, with a .197 on-base percentage, lowest in the National League. Tyler Moore, an outfield replacement with Jayson Werth on the disabled list and Harper shelved, finished the day hitting .136. Over the past two days, Nationals batters other than Harper, Ryan Zimmerman and Adam LaRoche are 5 for 42.

“It’s tough to be consistent when you have guys in and out of the lineup all the time, myself included,” Zimmerman said.

Nothing about Stults’s repertoire suggested he could oppress a lineup. He had a 4.57 ERA and had allowed 10.1 hits per nine innings this season, better than only 13 National League starters. He had stuck out 6.2 hitters per nine innings, well below league average. He throws his off-speed pitches — a slider, curve and change — more than half the time, and his fastball travels at 86 mph, not quite fast enough to send Doc Brown’s DeLorean back in time. In 2010, Stults started 21 games and posted a 5.07 ERA for the Hiroshima Carp.

Johnson’s abridged plan against Stults: “Don’t chase the junk.” Stults would try to establish fastball, and then get hitters to flail at pitches out of the zone.

“We were just swinging at his pitches and being not real patient,” LaRoche said. “He seemed to get us to chase all night.”

Stults did not allow a hit through five innings, despite a close call when Denard Span’s liner deflected off his wrist and straight to first base. For the final out of the fifth inning, Stults twirled three consecutive change-ups at Espinosa. He fouled away the first two. On the third, as it bounced in the dirt, Espinosa lunged and flung his bat down the third base line. As Espinosa’s lumber rolled into left, Stults walked off the mound 12 outs from a no-hitter.

“We’re just not doing the things we’re capable of doing offensively,” Johnson said. “We’re not hitting very smart. We’re swinging at his change-ups at the knees or in the dirt. We’re not making him throw the ball over. That’s a sign of some inexperienced hitters. You got to be more patient against a guy like this. We’re still growing as an offense. Don’t try to hit a pitcher’s pitch. That’s been some of the problems all year offensively.”

Finally, in the sixth inning, Kurt Suzuki led off with a laser into right-center field for a single. No longer in fear of infamy, the Nationals went about trying to score. Zimmermann pushed Suzuki to second with a sacrifice bunt. Steve Lombardozzi walked to the plate six for his last 52, then whistled a two-out single into right field. Suzuki scored without a throw and tied it 1.

All game, the Padres responded to Zimmermann’s aggression with more aggression, swinging early in the count and attacking fastballs. It worked once. In the second, Yonder Alonso crushed a 1-0, 92-mph fastball 365 feet down the left field line to give the Padres a 1-0 lead. Mostly, though, it allowed Zimmermann to buzz-saw his way through the Padres’ lineup.

In the fourth inning, Zimmermann dispatched the Padres in four pitches. He walked none and moved a three-ball count only once; after he went 3-1 to Chris Denorfia in the fifth, he threw a fastball on the next pitch and Denorfia flied out to right. After six innings, he had tossed only 60 pitches.

“That’s perfect for me,” Zimmermann said.

And so, the game entered the eighth tied at 1. John Baker led off with a single. Pinch hitter Alexi Amarista dropped down a bunt, but Suzuki pounced on it and fired a bullet to second base, a risky and successful play.

Now Zimmermann had to keep Amarista off first base. He threw over once. He threw over again, rocketing the ball to first as he spun on the mound. He pulled the throw, and as it bounded down the line Amarista scooted to second base.

“The throwing error by me cost us,” Zimmermann said. “If I don’t make that, we’re still out there playing.”

On cue, Cabrera followed with a single to center. Amarista slid home, well before Span’s throw bounced into Suzuki’s glove.

“To hand them a run — and the winning run — is never easy,” LaRoche said.

The Nationals wouldn’t score again, right up until the final failed rally. Lombardozzi drew a walk off closer Huston Street to lead off the ninth. After Zimmerman worked a 3-2 count, Lombardozzi bolted to steal second. Zimmerman whiffed at Street’s sneaky, 3-2 curve, and Lombardozzi slid into a tag. Another inning had ended with a whimper.

“I got my best up there, 3-2 count,” Johnson said. “I’m expecting us to put it in play. I’d do it every time. We’re just not doing the things we’re capable of offensively.”