You never want to wake up a sleeping giant, even if you are the Giants.

With one wild throw Monday, San Francisco may have awakened the team with the National League’s best record: the Washington Nationals, who accepted that gift and used it as the fulcrum of their 4-1 victory in Game 3 of this National League Division Series.

A moment arrives in many postseason baseball series in which one team is behind in games, clinging to playoff life, and the string of zeroes beside that team’s name on the scoreboard seems to stretch back as long as that team can remember. In October, what is really a minor slump suddenly seems like eternity.

For Washington, that line of zeroes, extending back to the third inning of Saturday’s Game 2, looked like this, at least in the Nationals’ minds: 000-000-000-000-000-000-000.

Yes, the Nats would score again, but if you’ve seen team after team expire in the clutches of the October Slump Monster, you suspected that next run might arrive next spring in Viera, Fla.

The Washington Nationals celebrate Monday’s win and discuss the game, from Doug Fister’s pitching to Wilson Ramos's game-changing bunt. (Whitney Leaming/The Washington Post)

Then, the Giants let their prey escape — for a day or perhaps for considerably more than that.

“We had a ball bounce our way today,” said Doug Fister, who threw seven scoreless innings in a victory that cut their deficit to two games to one. “We needed one little thing to jump our way, and it did.”

That bounce, that break, was more than a little thing; it was a symbolic play. The Giants had won 10 straight postseason games because, at least in October, they create the impression they never make fundamental errors, lose their poise for an instant or make mistakes in sensible split-second baseball judgment. In other words, they are clutch in that vague way that some teams, some veterans always seem to have an extra eye, a clock in their head that tells them where to throw, how hard to press their advantage.

The two most central Giants on a depleted roster that has battled for months to resuscitate a deteriorating season are former NL MVP catcher Buster Posey and ace southpaw Madison Bumgarner, the only star hurler still healthy from the Giants’ World Series wins in 2010 and ’12.

On one play, they both blundered. The first mistake was by Posey, who screamed “third [base]” rather than “first” as Bumgarner fielded a sacrifice bunt attempt by Wilson Ramos in the seventh inning of a scoreless game. Perhaps Posey sensed this was a “dagger” moment. Throw out the lead runner, force the Nats to pinch-hit (Ryan Zimmerman) for Fister, escape the inning with another “zero” and then get into the Nats’ bullpen. He thinks that fast, senses the momentum of the game that well. But he overplayed his hand.

The second mistake was both physical and mental. Bumgarner turned to third, saw he had no chance to throw out the swift Ian Desmond and, instead of ignoring Posey and throwing out Ramos at first, gunned the ball to third base anyway — and threw it wildly, too.

As the ball rolled far down the left field line into the confusion of the Giants’ bullpen, a goofy parade worthy of Market Street broke out on the bases. The Nats barely knew where the ball was. Third base coach Bob (Wave ’Em) Henley said, “I didn’t know exactly where the ball was, but I knew they didn’t have it,” and he started sending everybody in sight. “I couldn’t pick up Desmond” out of the dirt, but “I yelled as loud as I could.”

Bryce Harper needed less encouragement, flying home for a 2-0 lead. More than the ice was broken. The Giants’ mystique also had shown its first major crack in this series.

Asdrubal Cabrera plated Ramos with an RBI single shortly thereafter. And Harper — who had a superb game with two superior catches in left field, a walk and a run scored off Bumgarner — added an incredible insurance home run in the ninth inning with a blast, perhaps 425 feet, entirely over the right field bleachers beyond the 365-foot sign.

Before Harper’s blast, Giants fans behind home plate started to chant, “What’s wrong with Harper?” Answer: “He’s a bum.” Just as they finished their second chorus, Harper’s bat gave a shivering “CRACK.” The fans went silent, except one who simply said, “Whoa!”

That may be how the Giants feel, to some degree, too. After that two-run mistake, the Nats played with flair. Desmond showed off his gun arm at shortstop, while three Nats hit long drives that were caught. The Nats’ slump in this series is likely over, especially because the Giants’ Ryan Vogelsong is a crafty but make-do starter in Game 4. He will face Gio Gonzalez, who has been good recently but was nervous to the brink of implosion in two playoff starts in 2012.

Momentum has turned in this series. The Giants don’t want to face a Game 5 in Washington with Stephen Strasburg and Jordan Zimmermann available. But can Gonzalez get them there? The Giants, without regulars Angel Pagan, Marco Scutaro and Michael Morse, now use six lefty hitters against right-handers. Against Gonzalez, the Giants may be forced to a weaker lineup with right-handed hitting rookies or disadvantaged lefties. Even Nats Manager Matt Williams, who seldom points out rivals’ weaknesses, mentioned it vaguely.

“There’s still a lot less pressure on them. They’re still up,” said Nats first baseman Adam LaRoche, adding that decent ninth-inning work by closer Drew Storen had value. “He needed that, too, after the other night,” said LaRoche, referring to Storen’s blown save in Game 2 that still looms as an eerie glowing night light behind the rest of this series.

So the Giants make mistakes, too? “How about that,” LaRoche said. “That’s baseball.”

Ramos was this game’s hidden hero for getting down a sacrifice bunt toward first base with two strikes after taking two pitches right over the plate while in a bunt posture that seemed extremely foreign to him.

“That might be the first bunt of his career. I haven’t even seen him do it in batting practice,” Denard Span said, laughing. Henley actually whispered the signal into the ear of Ramos, whose last successful bunt was in 2011.

Conspicuous valor went to Harper, who made a racing catch in left-center a step from the 382-foot sign with two men on base in the second inning, then a one-on, one-out, face-first sliding catch to rob the Giants of a hit.

“Those are probably the two best catches I’ve seen him make all season,” said Span, who certainly has had the closest view all year. “He’s been tentative with the walls since last year in Los Angeles. He kind of shies away. But he had no fear and made an unbelievable play. The second [catch], he came flying out of nowhere.”

An appreciative Fister said Bryce “is sacrificing. He’s stretching and catching and rolling on the ground. . . . We had our backs against the wall, and we came out swinging.”

Aren’t you glad sports cliches aren’t dead? And that they are meant as dead seriously as in 1914?

The first major psychological damage in this series was inflicted when the Giants won games started by Strasburg and Zimmermann in D.C., where the Nats have the second-best home record in the sport. This game was half of a rebuttal as Bumgarner by the Bay has been the Giants’ best October knockout punch.

“Still got a lot of work to do,” Span said. “We gave ourselves a chance.”

In October, a terrible creature, universally feared but seldom defeated, attacks talented but increasingly nervous teams as one scoreless inning after another strangles their hopes of a long, glorious postseason. Call it the Pressure Monster or the Tension Tapeworm. Playoff watchers have seen it countless times but can count on their fingers the teams that escaped. The Nats just did.

But those Houdini acts usually require outside help. From your psychiatrist. From a ball lost in the sun. From a pebble in front of third base like the one that won the 1924 World Series for the Senators. Or a throw such as Bumgarner’s.

Now it is the Giants who may notice their offensive struggles. In 36 innings in this series, they have just six runs, five of them earned, and just two of them while a Nats starting pitcher was actually standing on the mound. The Nats’ team ERA is now 1.25. Excellent staffs usually grind down good batting orders in October.

Next up: Gonzalez. It’s only an elimination game for the Nats. But savvy as they are, the Giants know the true stakes. Tuesday is not their last stand. But they will be wise enough to treat it as such.

For more by Thomas Boswell, visit washingtonpost.com/boswell.