8:09 PM ET

ST. LOUIS — Jean Segura‘s career spanned 11 seasons and 1,328 games before he finally reached the postseason, the longest active streak in the major leagues. On the morning of his first playoff game, the Philadelphia Phillies‘ second baseman barely slept. He awoke at 7 a.m. “with adrenaline in my body.” Friday wore on, and that edge never left.

“I was mentally focused on every play, every pitch,” Segura said. “I came prepared today to play a game, and to be able to be here — I just thank God that everything was on my side.”

With the Phillies down a run, the bases loaded, one out in the top of the ninth and the St. Louis Cardinals scrambling to replace their wounded closer, Segura snuck a grounder past a slightly drawn-in infield, plating two runs and propelling the Phillies to an improbable 6-3 win in the opening game of their best-of-three wild-card series, putting them on the cusp of advancing into the National League Division Series.

The Cardinals, backed by a stellar performance from Jose Quintana and an electrifying pinch-hit homer by Juan Yepez, held a 2-0 lead heading into the final inning and had every reason to believe they were headed toward a Game 1 victory. They were at home, with a sold-out Busch Stadium crowd in a frenzy, and their lights-out closer, Ryan Helsley, was on the mound.

What followed strained credulity.

The Cardinals were 93-0 in postseason history when leading by multiple runs entering the ninth inning. The Phillies, meanwhile, were 0-54 during the regular season in that same situation. They wound up scoring six times — the most by a team trailing entering the ninth in postseason history. None of their runs came on hard contact. Alec Bohm was plunked with the bases loaded, Brandon Marsh hit a chopper that bounced past the glove of Nolan Arenado, Kyle Schwarber produced a sacrifice fly and Bryson Stott brought in a run after Paul Goldschmidt made a diving play on his grounder but threw late to home.

The biggest runs came off the bat of Segura, who lunged toward a slider low and away from Andre Pallante and hit a four-hopper to the right side that snuck through a sprawling Tommy Edman, who was playing slightly in to account for Segura’s speed. The Cardinals had a ground ball pitcher against a ground ball hitter and got a grounder that could have produced a game-ending double play — but it was hit just a tad too far to the right.

“That’s just kind of how the inning went,” Arenado said. “It wasn’t going our way.”

And it all seemed to stem from Helsley’s right middle finger, the one he jammed while gathering himself on a fielding play in the penultimate game of the regular season. Helsley threw some pitches off the mound during Thursday’s workout, and though he admitted to his finger feeling slightly stiff, he informed the Cardinals that he would be ready to close out games in the postseason.

Cardinals manager Oliver Marmol turned to Helsley with one on and one out in the eighth and watched him make quick work of Marsh and Schwarber. Shortly after the ninth inning began, though, Marmol said Helsley “started to lose a little bit of feel for his pitches.”

Helsley, who emerged this season as one of the sport’s most dominant closers, began to miss well wide of the strike zone and ultimately threw only nine of his 23 pitches for strikes in the ninth. J.T. Realmuto contributed a one-out single, then Bryce Harper and Nick Castellanos drew back-to-back walks, the latter on pitches that were either way up and in or way low and outside. By that point, the Cardinals had Pallante and Jack Flaherty warming in the bullpen. Bohm would be Helsley’s last batter — and Helsley hit him on the left shoulder with a 101 mph fastball.

After throwing a warm-up pitch well outside, Helsley exited, then departed Busch Stadium to get imaging done on his troublesome finger.

He might be lost for the series.

“We’ve had guys step up all year,” Marmol said. “If he goes down, someone else has to step up and do that job, so it’s part of it. No one’s going to feel sorry for us, I’ll tell you that. “

Friday’s top of the ninth marked the only half-inning in baseball this season where a team allowed at least six earned runs on three hits or fewer, with no extra-base hits allowed, according to ESPN Stats & Information research. There have now been five games in postseason history in which a team that led by two or more runs after the eighth inning lost by two or more runs — and the Cardinals have been involved in three of those. It marked the first time the Phillies had scored six or more runs in any postseason inning.

They picked the perfect time.

“It was special,” said Zack Wheeler, who threw 6? scoreless innings against the Cardinals, exiting three batters before Jose Alvarado gave up the two-run homer to Yepez.

“That was probably the most exciting inning I’ve ever been a part of,” Realmuto said of the top of the ninth. “And it didn’t even take a big home run. The momentum was there for us and multiple guys stepped up when they needed to.”