DUNEDIN, Fla. — Within a 30-foot radius in the Toronto Blue Jays’ cramped spring training clubhouse are locker spaces adorned with the nameplates Guerrero, Biggio and Bichette. Any baseball fan of the 1990s and early 2000s would recognize these surnames: Vladimir Guerrero, Craig Biggio and Dante Bichette combined for 20 All-Star Game appearances across two decades. But these lockers belong to Vladimir Guerrero Jr., Cavan Biggio and Bo Bichette, who have combined for zero big-league at-bats to date. They are on the cusp of the majors, prospects invited to camp in the sleepy Gulf Coast town of Dunedin, Florida.

But expectations are high for the Blue Jays’ young trio. Guerrero is the No. 1 prospect in the game according to most evaluators. Bichette is considered a top 20 prospect. And Biggio dramatically elevated his prospect status last season. Another son of a former big leaguer, pitcher Mark Leiter Jr., was also in the clubhouse before undergoing Tommy John surgery.

Second-generation prospects are not limited to the Toronto system, either. ESPN’s Keith Law has San Diego’s Fernando Tatis Jr., another legacy, as the game’s No. 1 prospect, while Pittsburgh’s Ke’Bryan Hayes — son of Charlie — is also a top 20 prospect. And numerous legacy prospects are or will soon be contributing to their big-league clubs: Adalberto Mondesi (son of Raul) is expected to be in the Royals’ starting lineup, Lance McCullers Jr. is a fixture in the Astros’ rotation when healthy, and slugger Cody Bellinger (son of Clay) has already earned an All-Star nod for the Dodgers.

If it seems like the kids of former big leaguers are taking over the sport this spring, it’s because they kind of are — they’re making the majors at rates far greater than the general population.

Whether it’s Guerrero, Bichette, Biggio or another prospect, the next child of a major leaguer to reach the majors will set a record for legacy debuts in a single decade. Entering 2019, the 2010s (44 debuts) are tied with the 1990s for most such debuts, according to Baseball-Reference.com data analyzed by FiveThirtyEight. The share of debuts by sons of major leaguers this decade is the second-highest on record (2.1 percent), and could perhaps challenge the 1990s record (2.3 percent) by the close of the season.

But it’s how the progeny of former players are reaching the pinnacle of the sport, and at increasing numbers, that is misunderstood.

“There’s a lot of misconceptions,” said Zach Schonbrun, author of the “Performance Cortex: How Neuroscience Is Redefining Athletic Genius.” “Everyone thinks two great athletes are going to come together and they are going to have a kid, and that kid is automatically going to become a superstar. It’s not so easy.”

Imitation game

When Cavan Biggio and his brother, Conor (who was drafted by the Astros in 2015), were in elementary school, Craig Biggio picked them up from school when the Astros were at home. They traveled straight to Minute Maid Park for the Astros’ pre-game batting practice. During games, Cavan and Conor didn’t spend their time in the family section; rather, they confined themselves to the Astros’ concrete bunker of a batting cage in the bowels of the stadium. They would hit off the tee and play games in the space, only vacating it if an Astros bench player came to get ready for a pinch-hitting at-bat. They observed the swings and collected the balls swatted into the nylon netting. The only other time they would pause is to watch their dad’s at-bats when their attention turned to the bubble-screen TV attached above the cage.

Like his dad, Cavan has a two-handed finish in his swing. This is not a coincidence. “The only thing he would say to me, mechanically, was ‘Two-handed finish, two-handed finish,’” Cavan said. “I still hear it today ‘Two-handed finish’ OK. I know [Dad]. I got it.”

He’s not alone in mimicking what made his dad so successful. The swing of Bo Bichette is also similar to his father’s.

Vlad Jr.? Like father, like son:

It’s not just at the plate, too. In Pirates camp, Hayes is renowned for his defensive ability at third base. “My mom says that our mannerisms on defense, the way we stand and stuff like that, are exactly the same,” Hayes said.

Driveline Baseball’s Kyle Boddy studies athletic movement patterns and is on the vanguard of player development in baseball. In speaking with Boddy for reporting on the “The MVP Machine,” he said the greatest advantage in being the son of a major leaguer is in mimicking movement patterns. After all, early-life imitation is key in motor learning. He cited the throwing motion of Astros’ McCullers Jr., which closely resembles that of his father’s.

Boddy suspects the children of major leaguers succeed at abnormally high rates. With the available data it’s difficult to know exactly how their success rate compares to the general population, but there are suggestions that it’s far better.

The proportion of U.S. high school players compared to domestic-born major leaguers has stayed more or less the same. In every year since 1978, there have been almost exactly 500 high school players in the country for every one U.S.-born major leaguer, according to Baseball-Reference.com and National Federation of State High School Associations data. That’s a success rate of about 0.2 percent. We don’t know the total number of major league progeny playing baseball, so we can’t make a direct comparison. But, over the last 30 years, the sons of majors leaguers have accounted for 2 percent of all debuts, and that number has gradually risen throughout the game’s history.

Pirates general manager Neal Huntington said Hayes’ pedigree played a role in moving him up their draft board, selecting him in the first round in 2015. Huntington is also confident the Blue Jays are “baking in” legacy considerations to their evaluation sauce.

“There’s a lot to be said for seeing how things are done at the highest level whether it’s motor learning or whether it’s how people carry themselves,” Huntington said. “They see the drive, the work ethic it takes.”

What’s also interesting about Hayes, Biggio and Bichette is not just what they observed but how they were taught.

“I never really worked on mechanics,” says Hayes about his father’s tutelage. “ At a young age, I just kinda learned the right movement, the fundamental stuff.”

Said Bichette: “We didn’t do a lot of drills.”

Boddy is wary of burdening pitchers with too many internal cues. Similarly, Schonbrun says implicit learning is the most effective way to acquire a skill.

“Ken Griffey Sr. probably didn’t show his son how to wiggle his bat and find that perfect arc for his swing,” Schonbrun says. “I’m guessing he probably told Ken Jr. ‘Here’s how you should get from A to B,’ and Ken developed that swing on his own. … In a lot of ways, that’s a better way for the brain to learn rather than following really detailed explicit instruction.”

‘Specialization’ is not a dirty word

A common experience shared by Biggio, Bichette and Hayes is that they all grew up with a batting cage in their backyards. They all had access to travel baseball, equipment and facilities. Tim Lee, a professor of kinesiology at McMaster University in Hamilton, Ontario, believes that those factors are perhaps the greatest advantage in having a professional athlete for a parent.

“The relationship of the model to the learner is one of the important moderating variables in observational learning,” Lee told FiveThirtyEight. “My hunch, however, is that this plays a far less important role than does the availability of practice facilities and instructional opportunities.”

While those spaces speak to the financial edge that also comes with being the son of a big leaguer, the cages, lessons and tools allowed them to be exposed to not just high-level motor patterns but enabled them to log thousands upon thousands of reps.

In the backyard of their Houston home, Hayes estimates he took “anywhere from 400 to 500 swings a day.”

Said Bichette of life in the backyard swing incubator: “At one point in my life we would go into cage and count at least 200 swings.”

For his fielding work, Biggio said his dad taught him to throw a lacrosse ball off a wall to create unusual hops to improve his hands. Hayes was also taught the practice and still tosses a lacrosse ball off of a wall when killing time in the hallways of minor league clubhouses. It’s one reason he projects as having a 70-grade glove on the 20-to-80 scouting scale.

When Bichette was a freshman in high school, he was also an excellent tennis player, but his parents urged him to choose one sport. Dante Bichette understood the importance of specialization.

While there has been research and concern about sports specialization leading to injury and burnout, Schonbrun notes it’s difficult to excel without it. Florida State professor Anders Ericsson attempted to quantify the hours of specialization needed to become an expert in 1993, which Malcolm Gladwell later dubbed the 10,000-hour rule in his book “Outliers.” Schonbrun said specialization is “necessary.”

“From a cognitive and neurological standpoint, the more you can focus on one task, the more practice that goes into it, the better you are going to be,” Schonbrun said.

Baseball-Reference.com‘s database contains father-son pairs to play in the majors but it does not include minor league family history or other family connections. That means the advantage in growing up around the game is probably even more considerable than we’re showing here. Consider the case of another consensus top-five prospect this spring, a player who could be the next teenager to reach the majors: Tampa Bay’s Wander Franco.

While he seems like a natural, dominating older competition at age 17 last summer, he is also the youngest of three brothers — each named Wander Franco — who each play in the Giants organization. His father, another Wander Franco, pitched in the minor leagues. His uncles Willy and Erick Aybar played in the majors. His neighbor growing up in the Dominican city of Bani was Cleveland Indians infielder Jose Ramirez.

Franco IV was exposed to elite-level motor patterns when he was young, but he was also around people obsessed with baseball. There was a dry river bed near his neighborhood in Bani and that became their ballpark. They used whatever scrap they could find to create bases. They wound up a sock to use as a ball.

“It was all games, every day,” Franco told FiveThirtyEight through an interpreter.

The Rays gave Franco, the No. 1 international prospect in 2017, a $3.85 million bonus. “One of the things that helped us get comfortable with that level of investment was that he had grown up around the game,” said Chaim Bloom, the Rays’ vice president of baseball operations. “You see a lot of guys who have a tremendous amount of skill but don’t know how to apply it on a baseball field. The way that Wander was able to do that as an amateur was really, really rare.”

Franco might seem like a natural, but his story might be more about nurture than nature.

Genes do play a role in success, of course. Bichette said the “bat speed” he shares with his father cannot be taught. Biggio says he has better than 20-20 vision and so does his brother and father. There are things Guerrero Jr. does with that bat that are assuredly tied to genetics.

But in some ways they are all lesser athletes than their fathers. Biggio is not nearly as fast as his father. Guerrero Jr. is not built like his father listed at a 6-2, 250 pounds, where his father was 6-3, 235. As a shortstop, Bichette has a much smaller frame than his father, who was a slugging corner outfielder.

While they are the sons of former professional athletes, there are more talented natural athletes that never reach the major leaguers. Their advantages go beyond genetics, and for a variety of reasons, the advantage of being the son of a major leaguer is growing.