Here is how October began: with a game that started on a September evening, that ended four hours and 45 minutes later, with a 47-year-old starch-collared executive tearing up in his team’s clubhouse as his team — which he assembled — acted like 4-year-olds all around him, toddlers who had gotten into the Champagne.

“Baseball games are unbelievable,” said Dayton Moore, general manager of the Kansas City Royals and a George Mason University alum, after Tuesday night had turned into Wednesday morning. “You can’t script them out. It’s a different game every single night. You never know what to expect.”

That’s how we rise, then, on October’s first day, with this beautiful mess of an American League Wild Card Game to start things off, 12 innings that involved 41 players and ended with Salvador Perez’s how-did-he-pull-that single to left, a rip that scored a rookie utility man named Christian Colon from second base with the run that provided a 9-8 victory over the Oakland Athletics.

Go to bed early? Understandable. It’s a long month. Still: For shame.

“That’s the most incredible game I’ve ever been a part of,” said Royals Manager Ned Yost, who contributed with his own incredible (read: baffling) decision-making.

Kansas City will play on into October in the postseason for the first time since George Brett and Bret Saberhagen were stars and Ronald Reagan was president. (Ed Zurga/Getty Images)

“Incredible” does not necessarily mean “flawlessly played,” and each side had strategic questions to answer. But in the delirium of Kauffman Stadium’s home clubhouse, with beer and bubbly being sprayed at any who ventured forth, Moore was able to both reflect back and look ahead because his team — reminded at every turn that it had ended this town’s 29-year postseason drought — came back from a four-run deficit with three runs in the eighth off postseason stud Jon Lester, then another in the ninth against Oakland closer Sean Doolittle, who had been scored upon once in his past 20 outings.

Want more? The Royals will play the Los Angeles Angels of Anaheim in Game 1 of a divisional series on Thursday because pinch runner Jarrod Dyson stole third in the ninth inning to set up the tying run on a sacrifice fly, one of Kansas City’s seven stolen bases. The Royals won because a 21-year-old lefty who, five months ago, was a student at Texas Christian University, held the A’s scoreless in the 10th and 11th with dominant stuff and preternatural poise. The Royals won despite the fact that the same pitcher, first-round draft pick Brandon Finnegan, walked the leadoff man in the 12th, leading to Alberto Callaspo’s run-scoring single that put the A’s ahead.

“First postseason in 29 years?” Finnegan said. “I felt like I just ended it.”

End it? It’s just beginning. These wild-card games are only three years old, but we now know what they are, clearly: Game 7’s, merely thrown at the beginning of the playoff schedule. The World Series is still three weeks away, but what a palate cleanser. Any other playoff manager sitting at home Tuesday night, watching out of habit or torture — Hi, Matt Williams — was only reminded about the microscope/cauldron to come.

Had the Royals gone quietly, Yost would have been skewered, and he might still be, for mismanaging his pitching staff, starting by lifting starter James Shields after 88 pitches when he still held the lead. Shields had made 68 starts as a Royal. Times he had been removed before throwing his 89th pitch: Zero (0).

At that point, to face the left-handed Moss — not to mention the left-handed Josh Reddick behind him — Yost could have turned to Finnegan, by golly, a lefty. He could have turned to stalwart Kelvin Herrera, normally the seventh-inning man, and his 1.41 ERA. But he went with rookie Yordano Ventura instead. Ventura is a starter who threw 73 pitches on Sunday. Brandon Moss deposited his third pitch 418 feet to straightaway center.

“Ventura came into a game earlier this year and actually won it for us by throwing an inning and two-thirds of relief,” Yost said. “He was lights-out, and we got to that point where we just wanted to bring the gas. . . . We didn’t want to push Herrera two innings.”

The Post Sports Live crew debates whether the Nationals will be disappointed with anything less than a World Series title after the end of an incredible regular season. (Post Sports Live/The Washington Post)

Instead, Herrera relieved Ventura in the sixth anyway, and pitched 1 2 / 3 innings.

“Just one of those things,” Yost said.

One of those things? This entire night showed that, beginning now, there are no more “things” to be shrugged off. When Herrera and Wade Davis locked down the seventh and eighth innings, seemingly meaningless outs had weight. When Oakland Manager Bob Melvin decided to let Lester — who had a 1.56 ERA in last year’s postseason with Boston — keep going after he had allowed two singles and a run, there were ramifications that will last into the offseason.

“He just tired a little bit there at the end,” Melvin said. He was charged with six runs in his 7 1 / 3 innings, the runs that got “The K”, as this place is known, rocking again.

That can’t possibly cover it all. Oh, Eric Hosmer. And Perez. Each is 24, the first baseman and the catcher who have only known one organization. Down a run in the 12th, Hosmer lifted a one-out triple to left, and he tied the game — again — on Colon’s chopper of an infield single. With two outs and Colon on second, Perez came to the plate with a horrible eighth-inning at-bat still in his back pocket, a strikeout on a pitch off the plate with one out and the tying run at third.

“I worry about it because I want to help the team,” Perez said.

When he hooked his hard single off Jason Hammel into left, he had helped the team, the town. The Royals mobbed him, a throng that danced into the outfield grass. It was beautiful.

“That’s really special, to see them celebrate,” Moore said. “You’ve got memories of them before they signed, and in rookie ball and instructional league, with all the hope of being a major league player, and when they broke into the major leagues. . . . To see this, it’s pretty special.”

It is Oct. 1. And it’s already special.