ATLANTA -- Ronald Acuna Jr. knew it was gone once the ball left his bat.
He took two slow steps toward first base, dropped his hands to his side and trotted around the bases and right into the record books.
The 20-year-old's second-inning grand slam gave the Braves an early five-run lead that propelled them to a 6-5 victory against the Dodgers in Game 3 of the National League Division Series, staving off elimination on Sunday night at SunTrust Park. And in so doing, he became the youngest player to hit a grand slam in the postseason, ahead of Hall of Famer Mickey Mantle.
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Acuna's teammates in the home dugout called the home run. Then again, they always do.
"We all think that every time he goes up to the plate," Nick Markakis said. "He's just an unbelievable talent. He's been huge. We would not be in the situation we are now without him."
The slam almost didn't happen, because Acuna nearly walked before it. Buehler threw him three straight balls to start the at-bat, and the fourth pitch was called a strike despite appearing to be high and out of the zone. Manager Brian Snitker said that Acuna had a take sign on the pitch, and it was a good thing.
Acuna turned on the next pitch, a 98.1-mph fastball, and watched it sail into the seats. Buehler peeked over his left shoulder and winced. He knew it was gone, too.
And with that, Acuna wrote his name in the record books again. Mantle had been the youngest player with a postseason grand slam, hitting his as a 21-year-old in the 1953 World Series for the Yankees against the Brooklyn Dodgers.
Somebody is eventually going to have to tell Acuna who Mantle is. After the game, the young star brought the house down when he quipped to reporters that he didn't know who the Hall of Famer was, "because I wasn't even born then."
"I was just really focused on that at-bat, and thank God I was able to make contact," Acuna said in Spanish. "We just have to show up with the same mentality [in Game 4], be positive and try to get back to Los Angeles with the series tied."
Acuna hit 26 homers during the regular season, but Sunday marked his first career grand slam. The rookie is coming off a breakout season that saw him set a franchise record with eight leadoff home runs. He also hit home runs in five consecutive games during one stretch. Still, Sunday's hit was his biggest to date, and it's not really close.
"I have to rank it first of all the moments just because it happened in the playoffs," Acuna said. "And to be honest, that's what we've been working for this entire time since Spring Training: trying get to the playoffs."
It was Markakis who drew a four-pitch walk to open the eventful second, but Buehler bounced back by striking out Johan Camargo and Kurt Suzuki. Ozzie Albies showed some patience when he looked at a pair of pitches outside the strike zone, and it paid off with a single to center.
When center fielder Cody Bellinger bobbled the ball, Markakis took third and Albies scooted to second on Bellinger's ill-advised throw to third. It prompted the Dodgers to walk Charlie Culberson intentionally, loading the bases for Braves starter Sean Newcomb, who entered the game 3-for-72 in his career. Newcomb looked at four straight pitches out of the zone, and just like that, the Braves had their first run of the series. It was the eighth bases-loaded walk issued to a pitcher in postseason history and it set the stage for Acuna's heroics.
"I was just up there waiting to see a strike and didn't get one," Newcomb said. "It was crazy. It was pretty exhilarating. I'm not used to holding a bat; I'm used to holding a ball. [After the walk] I was just trying to get down to first and not look stupid."
Freddie Freeman's solo home run in the sixth inning proved to be the game winner, but it was Acuna's blast that provided most of the offense. He is only the fourth rookie to hit a grand slam in the postseason, joining Paul Goldschmidt in 2011, Ricky Ledee in 1999 and Gil McDougald in 1951.
"You don't see somebody that young doing the things that he is doing, and we are just lucky to have him on the same team," Ender Inciarte said. "I'm always telling him to work and to stay healthy because the things you are going to be able to do in this game are not just good for you, they are great for this team."