PEORIA, Ariz. -- The Padres knew Fernando Tatis Jr. was a special talent from the moment he arrived in June 2016. They didn't know just how special until one September afternoon in Tempe.
As a 17-year-old shortstop, Tatis had wowed scouts all summer with his easy athleticism, big league frame and smooth swing. But that was in Rookie ball. This was instructional ball, featuring the best young talent from every organization.
In the first inning that day, Tatis smashed a single and stole second then third on the next two pitches. In his next at-bat, he singled and stole two bases again. In his third at-bat, he launched an opposite-field home run. For good measure, he added an excellent defensive play.
"He just took over the entire baseball game," said one member of the Padres' player development staff. "He was so clearly the best player on the field that day. Then there was a week's worth of it. He hit oppo home run after oppo home run, made play after play, and we were like 'Oh my God.'"
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The legend was born, though it took some time to make its way into the national consciousness. Tatis was still an unknown commodity, nowhere to be found on any prospect rankings.
Twenty months later, Tatis is the crown jewel of the Padres' top-ranked farm system. He's the presumed shortstop of the future for a team in search of one since Khalil Greene's departure a decade ago.
More than anything, Tatis symbolizes an organization that spent two seasons infusing itself with young talent through every available avenue. With those pieces in place, the Padres -- perhaps led by Tatis -- stubbornly believe they're destined to compete in the National League West for the better part of the next decade.
In June 2016, James Shields was coming off nine seasons with 200 innings and more than 30 starts. Reliable arms don't grow on trees, and Shields played a major role in the Royals' rebirth and push for the 2014 American League pennant. Tatis had yet to play in a professional game.
"You're always taking a risk on a player that hasn't played a game yet," said Padres general manager A.J. Preller. "The further guys are away from the Major League level, the harder it is to project. You have so much less information. We were giving up a proven Major League pitcher for a guy who hadn't played a game."
On the day of the trade, the White Sox sat two games back of Kansas City in the Central. The division was wide open. They needed a starter.
Preller, meanwhile, had begun tearing things down after his own ill-advised push for contention in 2015. The Shields trade was one of seven that year in which the Padres netted prospects for a big league player.
While working with the Rangers, Preller got his first glimpse of Tatis as a 14-year-old at a tryout. He vowed to keep Tatis on his radar, and when trade talks developed in 2016, the Padres sent scout after scout to White Sox camp.
"All the information basically came back the same," Preller said. "We had a chance to get an extremely talented prospect, even though he hadn't played a game yet, and he should be the target."
Video: Tatis Jr. is named the top Padres prospect
On June 5, 2016, the deal was finalized: Shields and cash to the White Sox for Tatis and Erik Johnson. Nearly two years later, Johnson is largely forgotten. But at the time, the 26-year-old righty was believed by some to be the centerpiece of the return.
Outside scouting circles, Tatis was on nobody's radar. He was merely the son of the man who once hit two grand slams in an inning.
"Most people didn't believe in me," said Tatis. "But they hadn't seen me play. What can I say? Now I'm playing baseball, I'm showing what I've got, and here we are."
It didn't take long for Tatis to skyrocket through the prospect leaderboards. Last season, he batted .281/.390/.520 and launched a franchise-record 21 homers for Class A Fort Wayne. At 18, he made the jump to Double-A and held his own during San Antonio's playoff run.
"When we got him, it was very clear that our scouts had done their homework on the raw talent," said Padres farm director Sam Geaney. "By instructional league, it was clear we had a pretty special talent on our hands. Going into 2017, we had a good idea that this guy was probably our best position-player prospect."
He's now widely regarded as one of the best in the game. Tatis is ranked No. 8 overall by MLB Pipeline and No. 2 among shortstops. The Padres already have begun planning their future around him, shying away from multiyear shortstops this offseason.
Instead, they traded for Freddy Galvis, who has one year remaining on his contract. That's not a coincidence.
Big league talent
On Feb. 16, Tatis reported to Peoria as the youngest player in any Major League Spring Training. A week later, in the Cactus League opener against Seattle, the righty-hitting Tatis drove a 1-2 fastball on the outside corner off the back of the right-field bullpen.
Video: SEA@SD: Tatis Jr. hits solo homer to right in the 8th
The organization had raved about his complete approach to hitting. It took two at-bats with the Padres for him to reinforce that notion.
"You hear about prospects coming up, and you can be skeptical sometimes," said Wil Myers. "Then you see it for yourself in person, and you know he's going to be a very, very good player. ... He's as good as I heard."
Tatis played 12 Cactus League games, starting often and facing the league's top pitchers. He went 4-for-4 against the White Sox (as if to rub salt in the wound of his former club). Two days later, he lined an opposite-field single against Madison Bumgarner.
In all, Tatis would bat .281/.343/.469 before being reassigned to the Minors on Tuesday. It might not be long before he's back for good.
Video: AJ Cassavell on the future of the Padres' infield
The Padres conclude their developmental seasons with a prospects game at Petco Park. In 2016, they beat the Rangers in Tatis' first game at his future home stadium.
In the clubhouse afterward, Tatis addressed the team unprompted. He told his teammates not to let up in their offseason work and that he believed in the direction of the system.
"It was cool to see," Geaney said. "The emotional maturity and the personal growth, I think that was a point we all thought was significant -- to stand up in front of his peers and deliver that message."
The Padres haven't been shy about accelerating Tatis' path. He could earn a September callup this year, and he has vowed to be "knocking on the door" by then.
Next spring, Tatis could compete for a roster spot. And soon enough, he could anchor a young lineup that includes Myers, Eric Hosmer, Manuel Margot, Austin Hedges, Hunter Renfroe and Luis Urias -- all of whom are controlled through at least 2022.
"This is just the beginning," Tatis said. "We've got to grind every day now."
This is just the beginning -- for his own career, and perhaps the revitalization of the San Diego Padres.
AJ Cassavell covers the Padres for MLB.com. Follow him on Twitter @ajcassavell.