WEST PALM BEACH, Fla. — Juan Soto learned a lot about baseball in the past year: how to work on the field; how to blend in off it; and how, most noticeably and notably, to hit as well as any 19-year-old in history once May became September and his numbers added up.

But there’s a flip side to any ascent. Baseball learned a lot about Soto, too.

“I don’t understand why you’d ever throw him a fastball if you can help it,” said an American League scout, tasked with tracking the Washington Nationals, as he watched one of Soto’s at-bats this spring. “He was a generational hitter against fastballs at 19 years old, an all-time hitter for that age. So why keep trying?”

That may be the leaguewide thesis for attacking Soto, now the Nationals’ 20-year-old left fielder, nearing his first Opening Day, even if it feels as if he has been here all along: No more fastballs. Nothing up in the zone. Work the far, far edge of the low-and-outside corner and, whenever possible, pound that spot with off-speed stuff.

That already started toward the end of last season, once Soto went from being a surprise call-up to the first teenager to do this and that and then something else. Next he will replace Bryce Harper in the meat of Washington’s order, whether he hits third or fourth, and every scouting report will get more detailed. It’s a product of his rise and the challenge of his future.

Yet Soto isn’t so simple to pick apart. His greatest strength in his rookie season — and there was a list of them — proved to be plate discipline. He lays off pitches that are centimeters out of the zone. He walked 79 times, the most for a teenager since 1900, and showed he will either get what he wants or wait for it, swing at fastballs and be super selective with everything else. Eighteen of his 22 home runs came off fastballs, and he slugged .696 against the pitch, according to FanGraphs, but the Nationals aren’t worried about more curves or fewer strikes or whatever teams try to do.

They just want Soto to be Soto, down to the way he kicks dirt between pitches, and let the adjustments come.

“I’m looking at it like, all right, they pitched me right here [at the end of] last year, and maybe they are going to try the same,” Soto said. “I just think of it like that and try to figure it out.”

'Different kind of player'

This time last spring, as the Nationals prepared to head north from West Palm Beach, their outfield options looked like this: Harper, Adam Eaton, Michael A. Taylor, Howie Kendrick, Brian Goodwin and, if additional depth was needed, Rafael Bautista, Victor Robles, Andrew Stevenson and Moises Sierra.

Juan Soto was not among them. He was in minor league camp, mixed in with dozens of other teenagers, playing on back fields while the Nationals planned for a season without him. But he was crushing the ball. Matthew LeCroy, the manager of the Class AA affiliate Harrisburg Senators, wondered how Soto possibly could be in the minors long. Mark Scialabba, the team’s director of player development, watched Soto blast home runs into the netting over the right field fence. Soto began the season with the low-Class A Hagerstown Suns, though not before he showed what hid in Washington’s system.

“You’ve been doing scouting for 27 years, [and] when you see a different kind of player, in your heart you feel like he can do it at any level,” said Johnny DiPuglia, the Nationals’ vice president of international operations. “That’s what I felt about him when I saw him in spring training last year.”

So when that outfield depth thinned — with injuries to Robles, Eaton, Goodwin, Bautista and Kendrick — Soto got his chance in mid-May. He had played just eight games above Class A. In his second career at-bat, against the San Diego Padres, he hit his first home run on an elevated fastball from Robbie Erlin.

A lot more of those came. Soto wasn’t a secret anymore. And neither was the best way to approach him.

“He’s a quick learner. He gets it. But that’s one part of the game that he knows we’re going to have to address,” Nationals hitting coach Kevin Long said in December. “Because they are going to throw him a lot more off-speed stuff, and he is going to be just fine. His mechanics are sound and his approach is sound enough where he is going to be good.”

'Look for fastballs'

Pick any spring training at-bat, no matter the day, inning or situation, and you can see Soto self-correct in real time.

Such as against New York Mets minor league reliever Tyler Bashlor, on March 17, once Soto already had homered in his first at-bat and doubled in his third. Bashlor got him to chase a slider in the dirt, and after hopping in the air, Soto looked at Long in the dugout and shook his head with a grin. Next, Bashlor threw a two-strike fastball off the outside corner. Soto leaned in to watch it, and once it passed, he twice pantomimed a half swing to get his timing down.

Then Soto widened his stance, with his cleats touching chalk on each end of the batter’s box, and wasted two breaking pitches by fouling them into the seats beyond the third base line. Then he got a full-count fastball and ripped a double into the right field corner.

“He knows there’s going to be some adjustments throughout the year, and he brings it up,” Nationals Manager Dave Martinez said. “Pitchers are probably going to try to do something different, and he’s aware of it. Just try to stay off the breaking pitches, look for fastballs. You don’t have to change anything. If you see a ball you think you can hit, swing at it.”

It is a simple science that is hard to master: Swing at strikes. Lay off balls, even the really close ones, and be cautious with anything that moves. Those pitches are harder to drive. Logic says so.

Soto followed all of that last year and, at his age, was comparable to (or better than) Ken Griffey Jr., Mickey Mantle, Alex Rodriguez, Tony Conigliaro, Mel Ott and Harper, the Nationals’ homegrown star who signed with the Philadelphia Phillies early in spring training. Soto has discussed improvements in left field and on the base paths. That’s what Martinez wanted him to focus on this spring. But he will be defined at the plate, in 2019 and always, well into Washington’s post-Harper era because he reset expectations by obliterating the initial ones.

“Everybody talks about it’s his second year, sophomore jinx, whatever you want to call it,” Martinez said. “My biggest thing with him is to stay in the strike zone and not try to do too much.”

At the end of another mid-March exhibition, after another towering home run, Soto answered a familiar round of questions in a quiet clubhouse. What’s the biggest change from last season to this one? How are pitchers throwing to you? How could you possibly get better at 20 years old?

Once the interview finished, Nationals pitcher Kyle McGowin approached Soto with a jersey and black Sharpie in hand. He asked Soto to sign it, right below the No. 22, and Soto joked that he couldn’t spell McGowin’s last name. Then he scribbled a short message and his fuzzy signature beneath it.

Who knows what that could be worth a year from now?