PHOENIX — Tonight, under the roof of Chase Field in downtown Phoenix, a scene few predicted months, weeks or even days ago will play out: The Arizona Diamondbacks will host Game 3 of the World Series.

How did Arizona shock the baseball world and get to this point?

It all starts with a young core led by right fielder Corbin Carroll and catcher Gabriel Moreno, a pair of 23-year-old emerging stars who arrived ready to play like seasoned veterans despite their age. The bright lights of October haven’t changed that.

“I think that’s what gets me excited about this team, not only for this year but moving forward,” Game 2 starting pitcher Merrill Kelly said. “You would expect in the years coming that all those guys … they’re already pretty close to elite players. And I think they’re only going to get better. That gives me excitement not only for going into this series, but also moving forward.”

It’s a sentiment felt throughout the organization. Most teams — this side of Baltimore, at least — wouldn’t be playing in October while starting four position players age 24 or younger, but that’s exactly what Arizona did in Game 2 of the World Series. In a 9-1 victory over the Texas Rangers on Saturday, Carroll, Moreno, 23-year-old Alek Thomas and 24-year-old Geraldo Perdomo combined for six hits, three RBIs and three runs scored — highlighted by Moreno’s fourth home run of the postseason.

Carroll, Thomas and Perdomo were all originally drafted or signed by the D-backs and climbed the minor league ladder together as part of a highly touted wave of prospects who had fans in Arizona hopeful better days were coming, even as Arizona lost 110 games just two years ago. It was Moreno’s arrival in an offseason trade with the Toronto Blue Jays that proved to be the final piece in turning that hope into what’s playing out now. He has become an elite player in his first full season, combining with Carroll to become the faces of the franchise who continue to outperform their age.

“Gabby is 23, but I feel like he’s 33,” Game 1 starter Zac Gallen said. “Just the way he’s super cool, super calm, collected. The moment doesn’t seem to faze him. And the talent is just off the charts.”

Exhibit A: Instead of being overmatched by his first taste of October, Moreno hit three home runs in his first five playoff games, off a trio of experienced postseason pitchers in Corbin Burnes, Clayton Kershaw and Lance Lynn. Exhibit B: He added another name to the list Saturday night when he broke a scoreless tie with a solo shot off a 3-2 curveball from Rangers starter Jordan Montgomery.

But power at the plate is just one part of his dynamic skills. Behind it, his game calling skills have gotten better and better while he already possesses one of MLB’s strongest arms.

“I joke that when I’m 50 years old, I’ll be watching Gabi Moreno still playing in the big leagues,” Kelly said with a laugh. “He’s that kind of talent.”

Reliever Joe Mantiply perked up when asked to pick the one moment that stands out from Moreno during the postseason.

“The homer against the Dodgers (in Game 3 of the NLDS),” Mantiply said. “He hits the home run foul and the next pitch, to be able to turn on one and hit another homer, that’s something only the best players in the world can do. That takes an unbelievable amount of talent and slow heartbeat to be able to execute in that moment. That’s probably the coolest thing I’ve ever seen on a field, to be honest.”

Moreno had already rounded the bases and was in the dugout when the umpires — after a delay — declared the would-be home run was a foul ball. On the very next pitch, he took Lynn deep — again. The smiles in the dugout were ear-to-ear as he circled the diamond again. It instantly became a signature moment for the young catcher and the D-backs, who hit a record four home runs that inning.

“I love playing,” Moreno said through the team interpreter. “I want to be there for my teammates as much as possible.”

In less than a year, Moreno has gone from playing in another organization to an essential part of Arizona’s future. The trade that brought him to the desert came as the result of a surplus of young outfielders in Arizona’s system and catchers on the Blue Jays’ major league roster. Because both sides were dealing from depth, several iterations of potential swaps were discussed. But as the D-backs did their homework, it became clear that Moreno was the player they wanted — and they were willing to give up Daulton Varsho, who produced 4.8 WAR with 53 extra-base hits (27 home runs) and 74 RBIs in 2022, to get their guy.

“What I heard back was essentially he was their Corbin Carroll,” Diamondbacks special assistant Jason McLeod said of Moreno. “That’s how they felt about him in terms of the person and makeup.”

That was an easy sell for the D-backs, who were well aware of the talent they had in Carroll, the heavy favorite for NL Rookie of the Year honors. His name has been in the No. 1 spot on prospect lists since he was taken with the No. 16 pick of the 2019 draft.

His teammates marvel at his maturity, saying he approaches the game like a grizzled veteran with a game that is more rounded than “most 30 year-olds.” It’s a theme heard often when talking to the veterans in the Diamondbacks clubhouse.

Though less heralded than Caroll and Moreno, Thomas and Perdomo have also impressed with their poise throughout October.

“Maybe it’s all in our DNA where we’re not really phased by it,” said Thomas, who hit a pinch-hit home run against the Philadelphia Phillies during the National League Championship Series. “Also, we learned from some negative moments during the season. And now on the big stage, we’re learning how to take a big breath and relax a little bit.”

Asked how the Diamondbacks have cornered the market on mature, young players, general manager Mike Hazen made it clear that it is no accident that their prospects arrive ready to perform in the majors.

“I think our player-development people do a really good job raising our players, quite frankly,” he explained. “We put a lot of effort into developing them all the way through from the second they get here to their families, to understanding who they are and trying to pour every ounce of energy into making them the best they can be.”

That process has paid off with a group making history with every feat as Arizona attempts to close out perhaps the most improbable playoff run ever. According to ESPN Stats & Information, the Diamondbacks are the third team in postseason history with a home run from four players 23 or younger. Moreno is also the youngest catcher to hit three home runs in a single postseason, let alone four.

With their young hitters seizing the moment, the D-backs have taken down two division winners and last year’s NL pennant winner. They’ve stolen home-field advantage from the hottest team in the AL. Mantiply — who was in High-A when he was 23 years old — was asked if he ever stops to appreciate what his young teammates are accomplishing this month.

“All the time,” he said. “Pretty much every day. I was fortunate to be around Alek and Corbin at the alternate site in 2020, when they were 18 years old. And the level of talent that they showed at that age was already unbelievable — and maturity. I remember thinking, Corbin specifically, was just on a different level of player that I’ve seen at that age. And the success that they’re all having is no surprise.”