Madison Bumgarner celebrates with teammates after his shutout victory in the NL wild-card game. The Chicago Cubs await in the NLDS starting Friday night. (Elsa/Getty Images)

It is October, and so the San Francisco Giants were celebrating on a baseball diamond, because when they get this far that is what they do. This time, the jumping jubilation was for a 29-year-old Nebraskan named Conor Gillaspie, and darned if he hadn’t just hit a three-run home run in the ninth inning of a scoreless game that would send the winner on and the loser home.

Up toward the plate ran Jarrett Parker, another anonymous Giant, who had been waiting in the on-deck circle to pinch-hit after Gillaspie. Bruce Bochy, the Giants’ manager, has seen just about everything. But as he watched Parker join the celebration, he nearly had a heart attack.

“Parker was there in the batter’s box high-fiving him,” Bochy said. Bochy yelled, waved, “screaming to get him out of there.”

The confusion: The umpire might have signaled that Parker, in the batter’s box, must be announced as the next hitter. And the next hitter had to be Madison Bumgarner, so he could finish off this game.

The Giants beat the New York Mets, 3-0, in the National League wild-card game with Gillaspie’s one swing of the bat, the homer off Mets closer Jeurys Familia with one out in the ninth. But they are a threat to take over October because of Bumgarner, the best postseason pitcher of his generation, now clearly one of the best in history.

Bochy’s panic attack came because, finally with a hard-earned lead, he needed Bumgarner to pitch that ninth inning. When he did, retiring the Mets easily in order, it completed a four-hit shutout in which no Met reached third base, in which he walked two (one intentionally) and struck out six.

“It’s hard to put into words what he did for us tonight and what he’s done for us,” Bochy said.

Record that sentence, then play it again the next time Bumgarner pitches. There is just no assailing his October performances. Half a century from now, they will be shown as relics not in grainy reel-to-reel black-and-white but in the brilliance of high definition. Will that keep our memories more clear?

Add this one to the list. Take the following seven games, likely the most important of Bumgarner’s career before Wednesday night: Game 4 of the 2010 World Series against Texas, when he was just 21; Game 2 of the 2012 World Series against Detroit; the wild-card game in Pittsburgh two years ago, when he threw a shutout; the first and fifth games of the 2014 World Series against Kansas City; and the full-on king-maker, the relief appearance against the Royals in the seventh game of that same series, when he threw five two-hit innings and was crowned a champion again.

Throw in Wednesday night, and the numbers are staggering. In 53 innings over those seven appearances, Bumgarner has allowed one (1) run, a 0.17 ERA. In that time, he has allowed all of 22 hits and eight walks, good for a .124 average against. When others cower, he mounts the horse, grabs the reins and yells, “Giddy up.”

“These are fun games,” Bumgarner said. “But they’re stressful at the same time.”

How could you tell? There was stress applied on the other side this time, namely by the Norse god named Noah Syndergaard, whose fastball lives at 98 mph, a hotter heater than anyone in the game. When Bochy, afterward, said, “It was all as advertised,” he was speaking of course of Bumgarner, but also of Syndergaard, because the 24-year-old is right there, ready to join Bumgarner as one of the best pitchers in the game.

He looked the part Wednesday, too. He struck out five of the first nine Giants he faced, setting them all down, and into the sixth, the Giants didn’t have a hit. When Denard Span finally singled with two outs in the sixth, Syndergaard rolled still, helped by Mets center fielder Curtis Granderson crashing into the wall after catching Brandon Belt’s drive to end the inning, keeping the Citi Field crowd alive, causing Belt to fling his helmet into short right field.

Syndergaard struck out 10.

“I’ve got to rank tonight as good as any [of his starts],” Mets Manager Terry Collins said, “under the circumstances.”

But the circumstances consisted both of Syndergaard’s pitch count, which was at 108 after seven, and Bumgarner on the other side. The Giants loaded the bases against setup man Addison Reed in the eighth, but Reed struck out Hunter Pence to end the threat.

Scoreless into the ninth, there was the sense that one swing would determine the outcome.

“But you can’t go out there and pitch scared,” Bumgarner said, “afraid to give up the home run.”

Whether Familia pitched scared or not is up for debate. But he allowed a leadoff double to Brandon Crawford, and when Angel Pagan couldn’t bunt Crawford to third, the game came to its fulcrum. With one out, Joe Panik expertly worked Familia for a walk. Gillaspie — who last year was with the White Sox and Angels but returned to the Giants, who originally drafted him, on a minor league deal — was in the game only because regular third baseman Eduardo Nunez was hurt, unable to be on the roster.

“It’s been, I guess, a little bit of a tough road for him,” Bochy said.

Yet Gillaspie’s at-bat was the key. If he failed to score the run, Bochy would have to pinch-hit Parker in an attempt to break the scoreless tie. If Gillaspie could drive one home, Bumgarner could pitch the ninth.

Familia threw Gillaspie a 96-mph sinker. And Gillaspie didn’t miss it.

“I’d be lying to you if I said I had the words to describe that moment,” Gillaspie said. “But, wow. I’m a lucky guy.”

Is he lucky? Or good? We now have that question again about the Giants, who have won World Series not only with Bumgarner as their hero, but with Cody Ross and Marco Scutaro and Travis Ishikawa, guys who could walk down Fifth Avenue in broad daylight and go unnoticed.

But here they come again, Bumgarner and the boys. The Cubs and their stars? This matchup could go either way, but don’t expect any Giant to quiver, regardless of their stature or status.