ST. LOUIS -- First, they squandered a four-run advantage. Then they frittered away a three-run lead. But the Giants had one more game-changing swing to offer, and it came from Kevin Pillar, whose two-run, eighth-inning homer lifted San Francisco to a 9-8 win over the Cardinals at Busch Stadium.

The victory snapped a four-game losing streak for the Giants, who entered Wednesday having scored one run on seven hits in the first two games of this series. But while the Cardinals tried to piece together nine innings from seven pitchers, the Giants’ offense showcased depth -- every starting position player tallied at least one hit -- and power.

• Box score

They needed every bit of it, too. The game featured four ties and lead changes from the fifth inning until Will Smith completed his first career four-out save. There were 40 players used, 365 pitches thrown and a combined 28 at-bats with a runner in scoring position.

“Entertaining game, wasn’t it?” Giants manager Bruce Bochy said after the four-hour, five-minute affair. “We just kept battling and found a way to win a ballgame against a good team.”

The evening provided its share of turning points, several of which drastically changed each club’s win probability -- which is calculated by FanGraphs in real time. Here’s a deeper dive into the most notable four:

Goldschmidt vs. Bumgarner

The Giants seemed to be sitting comfortably with a win probability of 88% after batting around to give starter Madison Bumgarner a 4-0 lead in the third. But the Cardinals pecked away, and eventually the moment led to another showdown between Bumgarner and Paul Goldschmidt.

There’s no one Bumgarner has faced more in his career, and the Cardinals’ first baseman came in with the advantage -- a career 1.012 OPS against the veteran lefty.

“I’ve faced him since basically my rookie year,” said Goldschmidt, who stepped to the plate in the fifth with the deficit at two and runners on the corners. “I’ve had some success, and other games he’s punched me out two or three times. It’s fun to go out there and compete against him.”

Bumgarner worked ahead, 0-2. Goldschmidt stayed alive by fouling off the next two pitches. After throwing a ball, Bumgarner’s sixth pitch was intended to be a curveball in the dirt, but it stayed up enough for Goldschmidt to drive. Jaylin Davis, in his Major League debut, couldn’t make the catch, and Goldschmidt cruised into third with a game-tying triple.

“He’s such a strong guy that he didn’t have any trouble hitting it out there,” Bumgarner said. “Sometimes, with the guy like that, sometimes it’s good to just concede the run and trade an out for a run at that point. But it didn’t work out that way.”

The hit dropped the Giants’ win probability to 36%.

An extra out

What should have been a routine third out in the top of the sixth became a gift-wrapped opportunity for the Giants when Cardinals shortstop Paul DeJong inexplicably changed his mind about what to do with the ground ball he had just fielded and subsequently didn’t get an out at all.

Brandon Crawford made it sting.

With a three-run blast on Dominic Leone’s full-count slider, Crawford propelled the Giants back ahead by three. It marked his first RBIs since Aug. 24 and his fourth go-ahead homer of the year.

“That [error] was huge, obviously,” Crawford said. “We did a good job all night of putting runs across, but that turned out to be a pretty big play.”

With the home run, the Giants’ win probability shot back up to 86%.

Goldschmidt, take 2

The Cardinals threatened that lead right away, chasing Bumgarner in the sixth and bringing the lineup back around to Goldschmidt. This time, Bochy opted to counter with Tyler Rogers. It was as contrasting a look as Goldschmidt could see, going from facing the left-handed Bumgarner to a side-arm-throwing righty.

“You’re ready for it,” Goldschmidt said. “Just make the adjustment and do the best you can.”

He never allowed Rogers a chance to settle in. On a first-pitch sinker, Goldschmidt delivered a two-run double to right to give St. Louis a lead.

“You don’t see a lot of guys come up first pitch off a sidearm thrower and be willing to sit back and shoot the ball the other way,” Pillar noted. “It’s impressive to watch.”

All of a sudden, the Giants’ win probability had sunk to 26%.

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Pillar makes an adjustment

Following an 0-for-3 performance on Tuesday during which he felt outwitted by the Cardinals’ battery, Pillar stepped to the plate in the eighth inning ready to cap a three-hit night with something more. He was to face reliever Giovanny Gallegos, who, with a fastball-slider mix, boasted the lowest ERA (1.29) by any Major League reliever since the All-Star break.

This time, Pillar felt ready.

“I tried to play that guessing game [Tuesday] night with [Cardinals starter Jack] Flaherty on the mound; it didn’t go so well with me,” he said. “I felt like every time I was looking slider, he threw fastball. Every time I thought fastball, he threw a slider. I tried to not bring yesterday’s results into today’s game.”

On Gallegos’ 0-1 offering, he thought fastball, and he got it. Pillar smashed it 440 feet for his 21st home run and 13th game-winning RBI of the year. The lead finally stuck.

“Our guys did a great job picking me up tonight when I didn’t do a whole lot for us,” Bumgarner said. “I’d like to make it a lot easier on our guys, but when you’re not very good and you don’t do a whole lot to help your team win and everybody else picks you up, that’s a good feeling.”