Anthony Rendon connects and reaches on a throwing error by Diamondbacks third baseman Jordan Pacheco, scoring Denard Span in the ninth inning. (Jonathan Newton/The Washington Post)

By the bottom of the ninth Thursday afternoon, rain had stopped dripping from the steel-gray sky above Nationals Park, and the Washington Nationals had turned a harebrained daydream into vivid possibility. Denard Span ambled back to first base after his flare fell into center field for a single. “Here we go again,” he thought. Arizona Diamondbacks first baseman Mark Trumbo greeted Span by shaking his head.

Trumbo said to him, “Just how you guys like it.”

The Nationals had crafted four walk-off victories in five days, and in a scoreless game Span had just created the chance for another. Moments later, after the biggest stolen base of his career and a misfire into the camera well, Span raised his left arm and trotted home with the only run of the Nationals’ 1-0 victory over Diamondbacks. The run perpetuated the most ridiculous stretch of baseball this town has ever seen, a winning streak that reached 10 games and infinite degrees of silliness.

When Jordan Pacheco fielded Anthony Rendon’s bouncer in the ninth and his throw bounded away from Trumbo, allowing Span to score from second, the Nationals had become the seventh team since 1900 — and the first since the 1986 Houston Astros — to notch five walk-off victories in six games. They also matched the longest streak in the team’s brief history, their first double-digit run since a halcyon fortnight in June 2005, their first year of existence.

“It’s indescribable, really,” Span said. “I really don’t have the correct or the right words to say what the feeling is other than saying that we just feel confident, that somehow, someway, we’re going to find a way to inch off a victory.”

Manager Matt Williams said he would hold to the vow he made early this season. It would not be appropriate now, he said, but someday Williams will tuck a pillow under his jersey and dust off his imitation of Babe Ruth calling his shot. “A promise is a promise,” Williams said.

The Nationals’ latest entry came without the benefit of an earned run or a hit with a runner in scoring position. But Gio Gonzalez’s seven scoreless innings lowered the rotation’s ERA to 1.34 during the 10-game run. Matt Thornton and Rafael Soriano threw two scoreless relief innings. They reenacted the joyous routine of streaming from the dugout and splashing water on teammates.

“It just wouldn’t be the same if we didn’t have a walk-off win,” Gonzalez said. “A perfect way to have a perfect 10. It wouldn’t be a Nats win without a walk.”

The 2014 Nationals have been a dominant team all season long. It took the magic of the past 10 days for their record to reflect it, for their luck to catch up to their NL-best, plus-102 run differential. The Nationals, who lead the National League East by seven games, have won twice in extra innings and seven games by one run over their winning streak. Before it, they had gone 5-8 and 13-18 in such coin-flip contests. A prolonged run of success was probably inevitable. It didn’t have to be such a giddily fun ride.

“Never seen anything like it,” said Thornton, an 11-year veteran. “It’s pretty special, pretty awesome. You can’t really describe it.”

The latest winning rally began with one out in the ninth, when Span flared a single to center field off lefty reliever Eury De La Rosa, the third time he had reached base. To face Rendon, Wednesday’s walk-off hero, Diamondbacks Manager Kirk Gibson summoned right-hander Evan Marshall.

Span had come to spring training “on a mission” to steal more bases this season, first base coach Tony Tarasco said. He stood on first with 26 for the season, tying a career high at age 30. If he could get 27, he would put the winning run in scoring position.

Tarasco informed Span that Marshall took 1.3 seconds to deliver his pitches. Tarasco knows Span can steal a base when the opposing pitcher takes more than 1.3 seconds. Anything quicker, he needs some kind of tell to jump early. Right on it, bolt and hope.

“We knew it was an opportunity where we were going to have to take a chance,” Tarasco said. “It was something he’s going to have to a little bit more courage with.”

One of Span’s best friends chides him about his “alter ego,” Span said afterward. He tells him “Denard” is the passive half of his personality, a man afraid to make mistakes. “Span” is the guy who makes aggressive plays, who can pick up a girl at a party.

“I guess it’s like the Urkel and the Stefan,” Span said.

As Marshall fired his warmup throws on the mound, Denard strolled off the base and talked to himself. When he returned to first base, he was Span.

“I was like, ‘Let’s go,’ ” Span said.

Marshall started Rendon with a slider, then a fastball. Span has the ability to stop himself when he gets a poor jump or notices the pitcher uses a delivery move to the plate, “which is something that he’s worked on tremendously,” Tarasco said. “Being able to keep your eye on the pitcher just a fraction or a hair longer.”

On Wednesday night, Rendon had singled home the winning run when Marshall threw him two straight fastballs. Span suspected he would throw a slider, a perfect pitch to steal against. Marshall lifted his leg. Span saw what he wanted. He bolted, and he slid spikes-first into second, ahead of Tuffy Gosewich’s throw. Safe — steal No. 27.

“That’s what guys like me, speed guys, dream of,” Span said. “That’s way more important than stealing two or three bags in first five innings. That was probably my first meaningful bag in my career right there, where I actually stole and put us in a position to win like that.”

With the winning run in scoring position, Rendon chopped a grounder to third. Pacheco played it on a high hop, stepped to first and fired. Rendon was sprinting. “I just ran,” Rendon said. “Like Forrest Gump.”

Trumbo stretched to scoop Pacheco’s one-hop throw, but the ball skittered past his glove and trickled away. The umpires ruled Span had sprinted close enough to third base to award him home.

In the first seven innings, the Nationals smacked eight hits, drew six walks and put six leadoff hitters on base. They also went 0 for 11 with runners in scoring position, stranded eight runners and failed to score a run. Arizona left-hander Wade Miley scrapped for 62 / 3 innings, executing huge pitches at critical moments.

Gonzalez, though, kept the Nationals in the game. In his previous two starts, Gonzalez had thrown 213 pitches over 92 / 3 fruitless innings. He couldn’t earn his first win since July 5, but Gonzlaez rebounded with his best start since then. He allowed four hits and three walks and threw only 97 pitches. He also recaptured his trademark curveball, using it three times for a strikeout in the final three innings.

“I tried to stay on top on the pitch,” Gonzalez said. “I wasn’t dropping my elbow or coming from my back pocket or anything like that. I was trying to snap it out in front, trying to get a good feel for it.”

Gonzalez watched the finish from inside the clubhouse. When Span singled, he thought, “We got it in the bag.” The improbable has become commonplace at Nationals Park. It is just how they like it.