Fans cheer above the St. Louis Cardinals dugout after a three-run home run by Ryan Howard #6 of the Philadelphia Phillies. (Drew Hallowell/GETTY IMAGES)

For a few nervous innings there Saturday night, the Philadelphia Phillies and their fans must have been wondering if the whole blessed thing — the construction of the greatest starting rotation in a generation, the 102-win march to another division title, the quest to cement the franchise’s status as the closest thing baseball has to a modern dynasty — was going to blow up in their faces before October was even one day old.

Their offense was being manhandled by a No. 4 starter masquerading, out of necessity, as a No. 1. Their own ace, the defending Cy Young Award winner, had given up his first three-run homer in more than three years, and had to labor just to close out the first inning. Citizens Bank Park had gone silent, as if this were 2006 again, with 46,480 white “rally” towels clenched in 46,480 fists on 46,480 laps.

It sounds strange to say now, in the wake of the Phillies’ thorough 11-6 undressing of the St. Louis Cardinals in Game 1 of the National League Division Series, but before Ryan Howard hit the three-run homer that put them ahead for good in the sixth inning, and before Roy Halladay turned back into Roy Halladay, retiring 21 batters in a row at one point with only one ball leaving the infield, the five-time defending NL East champions looked extraordinarily vulnerable.

“That was a good way to start the game,” Cardinals Manager Tony La Russa said of the 3-0 lead they took against Halladay in the first inning. “But we were saying in the dugout, ‘Three runs was not going to win the game.’ ”

The best chance the underdog Cardinals had to steal Game 1 slipped away from their grasps in the pivotal sixth inning. Holding a 3-1 lead, starter Kyle Lohse, a 32-year-old right-hander of modest ability, had one out and runners on first and second, with Howard coming to the plate representing the go-ahead run.

Ryan Howard hits his three-run homer in the sixth inning of Game 1 of baseball's National League Division Series. (Matt Rourke/AP)

Howard’s failures in the 2010 postseason were much-scrutinized in Philly — no homers and no RBI in nine playoff games — but what really mattered in this situation was the wide difference in his splits against right-handed and left-handed pitchers. Against the former group this season, Howard posted a .921 on-base plus slugging percentage; against the latter, .634 — a disparity roughly in line with his career splits. Against right-handers, he hits like Albert Pujols. Against lefties, like Robert Andino.

Lohse had thrown just 61 pitches to that point, hadn’t allowed a hit until the fourth inning, and was only facing this two-on, one-out situation because of a couple of cheap singles. The jam had happened so quickly, there probably wasn’t even time to warm up a lefty to enter the game. So La Russa left Lohse in to face Howard.

“Pretty tough to take him out there,” La Russa said. “My decision was based on what I had seen. I didn’t see [Lohse] do anything wrong.”

Lohse battled Howard valiantly, throwing five change-ups in an eight-pitch at-bat, including the last three pitches. Lohse would later say he was trying to throw them all out of the strike zone, hoping Howard would chase — and he did, fouling off a pair of 3-2 change-ups. But then Lohse made a mistake, leaving the last one over the heart of the plate, and Howard crushed it into the seats in right.

“We just knew it was just a matter of time,” Howard said.

Suddenly, the Phillies had a 4-3 lead, and all was right in their world. The stadium erupted, and from there the game quickly became a blowout. Raul Ibanez followed two batters later with another long home run before La Russa came to pull Lohse. The Phillies would tack on three more in the seventh and two more in the eighth against the Cardinals’ bullpen, perhaps demonstrating another reason why La Russa showed so much faith in Lohse during the pivotal sixth.

And meantime, Halladay was going on one of those dominating stretches, reminiscent of the one a year ago, when he no-hit the Cincinnati Reds in Game 1 of the 2010 NLDS. He was none too pleased with himself about the three-run homer he gave up to Lance Berkman in the first inning, which followed a four-pitch walk to Pujols. It was the first homer Halladay had given up all season with runners on base.

“He was kind of like a Rocky movie,” Manager Charlie Manuel said. “He got mad after he gave up that homer. . . . He hung in there and he got going.”

A mad Roy Halladay is not somebody you want to encounter. Nor is a redemption-seeking Ryan Howard, when you don’t have a decent lefty to send to the mound to face him. The Cardinals are finding out the hard way you only get one chance to beat these Phillies on this stage, and on Saturday night they missed it.