Matt Kemp a swing shifter for Dodgers in 3-2 win over Cardinals

At this stage of the season last year, Matt Kemp was on crutches, calling himself the Dodgers’ head cheerleader.

In the wake of the Dodgers’ 3-2 victory over the St. Louis Cardinals in Game 2 of their National League division series, Kemp can call himself something else: October hero.

Kemp’s eighth-inning home run Saturday night produced a triumph on a night when the Dodgers’ notoriously unreliable bullpen blew a two-run lead, giving the team a victory that tied the best-of-five series at one game apiece.

Kemp recognized the magnitude of the moment.

“This is big right here, man,” Kemp said. “This is a must-win for us.”

The Dodgers will travel on Sunday to St. Louis and resume play Monday at Busch Stadium.

“We can definitely feed off of this win,” Kemp said.

They figure to be in high spirits, considering what they overcame.

Clayton Kershaw imploded Friday night in a shocking 10-9 defeat in Game 1. A day later Zack Greinke did what Kershaw couldn’t, only for J.P. Howell to serve up a two-run home run to Matt Carpenter that erased the 2-0 advantage he inherited at the start of the eighth inning.

“It was an emotional roller coaster, but I’m happy it ended this way,” Howell said.

When Kemp stepped into the batter’s box in the bottom of the eighth inning, the 54,599 fans at Dodger Stadium were still in shock from the home run by Carpenter, whose three-run double against Kershaw put St. Louis ahead, 7-6, in Game 1.

Kemp changed everything when his bat crashed into a 2-1 pitch by Cardinals reliever Pat Neshek. The stadium roared as the ball soared high into the Los Angeles sky and into the seats by the left-field foul pole.

Kemp had waited long for this moment. Until this series, he hadn’t played in a postseason game in five years. Last year, he was sidelined with a fractured ankle that required a major operation over the winter.

“Just blessed, man,” Kemp said. “It’s been a grind the last two years.”

He hit 17 of his 25 regular-season home runs after the All-Star break, prompting catcher A.J. Ellis to call him the most valuable player of the second half of the season.

Still, Kemp figured he could be a game changer. He was also aware of how these playoffs could restore, if not enhance, his reputation.

“For sure,” he said. “The thing about it is, you get one big hit or one big play in the World Series or the postseason, people will remember that forever. You see how Derek Jeter is. You couldn’t write his script any better. His whole career he’s been a winner. Five World Series championships. He’s gotten a lot of big hits for them.”

Greinke nearly made Kemp’s heroics unnecessary.

The Cardinals didn’t record their first hit until the fifth inning, when Kolten Wong doubled down the left-field line with one out. Greinke struck out the next two batters, Randal Grichuk and pitcher Lance Lynn, to preserve his team’s 2-0 advantage.

Greinke encountered more serious trouble in the sixth inning, which Carpenter led off with a double to left-center field. Greinke forced Jon Jay to ground out and struck out Matt Holliday before walking Matt Adams. Then Greinke struck out Jhonny Peralta to end the inning.

That Greinke would respond like this was no surprise to Ellis, his catcher.

Ellis pointed to the role Greinke played in helping the Dodgers recover from a couple of potentially crushing defeats earlier in the season.

The first time was in mid-September, when they dropped the opening game of a three-game series against second-place San Francisco at AT&T Park. With the Dodgers’ division lead down to one game, Greinke responded the next day by pitching six scoreless innings in a 17-0 victory.

A week later, the Dodgers lost another series opener to the Giants, this time at Dodger Stadium. Again, Greinke pitched the second game of the series. Again, he won, limiting the Giants to two runs over eight innings.

Greinke also contributed offensively Saturday.

The Dodgers broke a scoreless tie in the bottom of the third inning, which Ellis led off with a double. Ellis finished the season with a .191 average but was four for five with a home run and three runs in Game 1.

Ellis advanced to third base on a single by Greinke. One at-bat later, Ellis scored to move the Dodgers in front, 1-0, when Dee Gordon grounded into what was initially ruled a double play.

But Manager Don Mattingly asked for a review using baseball’s expanded replay system to determine whether Greinke had been tagged out on the play by second baseman Wong. The initial call was overturned and Greinke was awarded second base, as replays clearly showed the ball was in Wong’s throwing hand when his glove touched Greinke.

The Dodgers were rewarded for contesting the play, as Greinke scored on a two-out single to center field by Adrian Gonzalez.

There was some controversy earlier in the game, as Yasiel Puig showed displeasure with a high fastball delivered in the first inning by Lynn. Puig, who was hit by a pitch in Game 1, exchanged words with catcher Yadier Molina before and during the at-bat.

dylan.hernandez@latimes.com

Twitter: @dylanohernandez