ATLANTA — The Atlanta Braves had played more than half of their schedule, they still had a losing record, and then things really got bad.

On July 10 in Miami, their best player, Ronald Acuña Jr., raced across the outfield grass for a deep fly ball in Miami. It was over his head but he leapt for it anyway, soaring at the warning track like a long jumper. Acuña landed hard on the dirt and could not get up.

Somehow, his team did. Acuña’s season ended that night in July with a full tear of his right anterior cruciate ligament, but for General Manager Alex Anthopoulos, the challenge was underway.

“I’m not an emotional guy where I throw things or get angry and yell and scream,” Anthopoulos said in an interview a few weeks after the injury. “I wish we had Acuña; he’s one of the best players in the game. It changes our chances, of course. You can’t replace Ronald Acuña. But I just don’t believe you can have the mind-set of: You lose any one player and you just shut it down for the season.”

Anthopoulos takes the same approach to team-building as his players do at the plate and on the bases. He is aggressive, and when he knows what he wants, he does not waste time. In July he wanted outfielders — needed them, really — so he traded for four: Adam Duvall, Joc Pederson, Eddie Rosario and Jorge Soler.

None were having especially good seasons, so the cost was low. But all had been productive in the recent past, and Anthopoulos believed one or more could make a difference.

“He hoped we had a chance, a big chance, to come back — and we did it for him,” said second baseman Ozzie Albies, who helped Atlanta rally to win a weak National League East. “He did a phenomenal job getting those guys for us and kept the team rolling.”

They have rolled all the way to the National League Championship Series, with Acuña cheering on his teammates in the dugout. On Sunday, when Acuña’s regular leadoff spot came around with two outs in the bottom of the ninth inning in Game 2 against the Los Angeles Dodgers, one of his replacements was ready.

“To be honest, it was a competition at first,” Rosario said through an interpreter late Sunday, after his fourth single of the night scored Dansby Swanson to finish a 5-4 victory, giving Atlanta a two-games-to-none series lead.

“All four of us showed up, and I think we all wanted to get some playing time and be in the lineup. And obviously the three guys, they were having success on the field, so for me it was definitely a little bit of a sense of urgency to try and work my way into the lineup as much as possible.”

Atlanta would not be here without him. In Game 1, Rosario led off with a single, stole second and scored on a wild pitch. In Game 2, his third single started a game-tying rally off Julio Urias in the eighth, and his fourth, a smash up the middle off Dodgers reliever Kenley Jansen, deflected off shortstop Corey Seager’s glove and into center field for the win.

It was the second game-ending hit for Atlanta in a row, a nice reward for fans who had waited 20 years to host another N.L.C.S.

“This is a team that you better not leave early,” said Manager Brian Snitker, who got the only gift he wanted for his 66th birthday on Sunday. “You’ll end up missing the best part of the game and listening to it on your radio when you’re driving home, because these guys never quit. They never have. They haven’t for years here.”

Maybe not, but as a franchise, the Braves are not known as the best finishers. Their 1990s juggernaut reached the N.L.C.S. eight times and won five pennants — but only one championship, in 1995. In this century, their luck has been worse.

No other franchise has reached the postseason as many times in the 2000s without a World Series appearance. This is the team’s 13th journey since their 1999 pennant, and last year’s was especially wrenching. In the neutral site of Arlington, Texas, they blew a three-games-to-one N.L.C.S. lead to the Dodgers, who went on to win the title.

This year’s series is playing out the same way, as Austin Riley, whose single won Game 1, said on Sunday night.

“We were up on them 2-0 last year, so it’s like one of those things where you can’t stop now, you got to continue to apply the pressure,” Riley said, adding later, “It’s in the back of your mind: They’re a really good ball club, they’re never out of it until the last say.”

Atlanta secured the last say in the N.L.C.S. by winning their division with 88 victories; the Dodgers had 106, but as a wild-card entrant, they opened on the road. With two losses already, the Dodgers would have to return here to win the series.

The Dodgers will start Walker Buehler on extra rest at home in Game 3, and Manager Dave Roberts said they would “lean on him” then. Perhaps, but evidence suggests otherwise. The Dodgers used eight pitchers in Game 1 and seven on Sunday, determined to confuse opposing hitters as much as possible.

When it comes to pitching strategy, the Dodgers are the slick street hustler and the opponent is the mark, certain to fall for their three-card monte act. It usually works, all that shuffling of arms, and some of Atlanta’s players — like poor Freddie Freeman, who is 0 for 8 with seven strikeouts — have been flummoxed.

But Atlanta’s hitters do not try to work deep counts and draw walks; they have walked only twice this series but have 16 hits, two more than the Dodgers, who are 2 for 18 with runners in scoring position.

“We knew coming in they’re very aggressive swinging the bat, especially early in the count,” Roberts said. “You’ve really got to make a quality pitch that first pitch.”

Pederson took the biggest swing of Game 2, turning on Max Scherzer’s 1-0 curveball in the fourth for his third home run of the playoffs. Rosario took the last swing, ripping Jansen’s first-pitch cutter for the game-winner, raising his postseason average to .409.

Anthopoulos’s other two outfield additions have not done much lately. Soler is out for the series after a positive test for the coronavirus, and Duvall — the N.L. leader in runs batted in for the regular season — is still seeking his first R.B.I. in these playoffs.

But Anthopoulos bought in bulk to replace the irreplaceable, and the pieces fit well together. October’s surge stemmed from July’s despair, and the newcomers who came to the rescue.

“We saw a difference right away,” Albies said. “The team clicks more and we started playing better ballgames, and that’s one of the main reasons we are here today.”