ST. LOUIS -- The inevitable blip, the defining moment of Boston Red Sox pitcher Jon Lester's evening unfolded in the fourth inning when he left a fastball out over the plate and watched Matt Holliday launch a rocket into the center-field seats.
Just like that, his Game 5 World Series shutout was kaput and Boston's 1-0 advantage was erased. And, when Carlos Beltran followed with a bomb of his own to the warning track in left-center, Lester knew what you were thinking, because he was thinking it too.
"I was kind of looking around and saying, 'Whoa, what's going on now?'" Lester admitted.
These are the moments in the World Series that separate the aces from the "quality" pitchers. How they respond to an inning that starts to break badly, to a singular moment that could easily spiral into a mound of trouble, tells you all you need to know about their physical and mental makeup.
As teammate Ryan Dempster explained, "Whenever you're facing an elite pitcher, you get one inning to get to him. If you do, it can change the game. If you can't, you've probably missed your chance.''
Lester understands how slim the margin of error can be. Had Beltran clobbered that ball to another part of Busch Stadium, it could have been a home run.
Lester retreated to the dugout, conferred with his trusted catcher, David Ross, then re-emerged as the most dominant player in Monday night's game.
After Holliday's homer, he retired the next 11 consecutive batters.
The St. Louis Cardinals didn't score another run.
The Red Sox left town 3-1 winners.
They come back to Boston up 3-2 in this series, one win away from being crowned 2013 World Series champions, and for that they can thank their redoubtable lefty, who went 7 2/3 remarkable innings fighting off growing tightness and discomfort in his back.
The adjustments Lester made following the fourth inning, said Ross, were the difference in the game.
"The thing that got him in trouble last year was he was getting underneath the ball and it would flatten out,'' Ross explained. "I think that's what happened with Holliday. It was a good pitch. It wasn't a terrible pitch.
"It was just kind of flat.''
As they tried to stay loose in the dugout, Ross reminded Lester to maintain his posture, to stay upright from front to back.
"I'm always talking to him about that,'' Ross said. "Work downhill. Stay tall. When he does that, he's almost unhittable.''
The Red Sox needed an ace performance from Lester because St. Louis had an ace of their own spinning his wares. Adam Wainwright's curveball was as equally filthy as Lester's back-door cutter.
For six innings, Boston could inflict only minimal damage on Wainwright and the Cards. It was an old-fashioned pitchers' duel, with all of baseball waiting to see who blinked first.
It was Wainwright, burned by the bottom of Boston's batting order in the seventh when he walked Drew and gave up a ground-rule clutch RBI double to Ross. And when Jacoby Ellsbury knocked in another RBI (after going hitless in his eight previous at-bats), Wainwright's night was over.
Lester, meanwhile, unleashed his curveball in the later innings, confounding the Cardinals with his changing speeds. He finished with 7 strikeouts and 0 walks.
"He's one of those big league lefties who can manipulate the baseball really well,'' Red Sox pitching coach Juan Nieves said. "Sometimes after he's thrown a light bullpen, I tell him, 'You know something? You don't have to use your body anymore.'
"When guys [like Lester] are that big and strong they want to throw harder with their body instead of working the baseball with their hand.
"But the more he does it, that light bullpen, with some touches and feels, he realizes, 'I don't always have to throw harder. I can manipulate this baseball.'
"You saw it tonight. He was able to slow the game down, speed the hitters up. That change of speeds, first 77 [mph] then 94, that's what makes Lester a great pitcher.''
Lester has been a "great" pitcher before. Exactly six years ago, he pitched 5 2/3 innings of shutout baseball and the Red Sox hung on to beat the Colorado Rockies 4-3 for a World Series sweep.
At the time, Lester was projected to be on his way to becoming one of the best left-handers of his generation. The next season, he threw a no-hitter against the Kansas City Royals.
But recent history has not been so kind to him. In 2011, he was at the center of Boston's collapse, named as one of the pitchers who indulged in chicken and beer and snuck into the clubhouse to watch football instead of cheering on his team.
Last season, he suffered through one of the worst years of his career, going 9-14 with a 4.82 ERA and serving up a career-high 25 home runs.
The turnaround has been pronounced, gratifying. It started in spring training when he arrived with a singular focus, and an understanding that he needed to be accountable for some past transgressions. Ross, who became his personal catcher, worked on his mechanics with him, and said, "I knew right away this guy was a stud. He just needed a few tweaks.''
His teammates quickly noted Lester's concentration and workmanlike approach.
"I had never played with him before,'' Dempster said, "but I could see it right away. In his first spring training game, he threw five no-hit innings. I said, 'Whoa, this guy wants it.'''
Eight months later, Lester and his team are one win from redemption.
"I just told Jonny Gomes in the clubhouse, I said, 'You know, you show up on Feb. 1, play 162 [games], we're probably at 180 now, and it comes down to one game,'' Lester said.
He is sore and stiff and exhausted and excited and yes, after all these years, he still gets pregame jitters when the stage is so big and the lights are so bright.
"It doesn't matter how many games you've played,'' Lester said. "Your nerves are going, your heart rate is going. But once you settle in, you realize, it's baseball. Fastball down and away. [In] Game 5 of the World Series it's just as effective as on Feb. 1."
That's how elite pitchers think.
The Red Sox haven't won a thing yet, but that hasn't stifled speculation regarding possible MVP candidates. If Boston wins the World Series, Lester would be a viable candidate, but his DH-turned-first-baseman is batting more than .700 ("What planet is he from, anyway?" Ross cracked), and as a result, David Ortiz is the odds-on favorite to take home some hardware.
Lester doesn't care. He was a World Series winner once, and has a chance to be one again.
After everything he has been through, that's more than enough.