MLB has its most productive class of rookie hitters ever; Managers and players believe they know why

Royce Lewis has played in 70 games for the Minnesota Twins. He has five grand slams.

The AL Central champion Twins haven't had a rookie so ready for major league stardom since Joe Mauer nearly two decades ago. Despite a decided lack of live games over the last three seasons due to injuries and the pandemic, Lewis entered the lineup after finishing his ACL rehab and immediately hit like he'd been there for years.

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"An impact on our team that we can't really measure, except to say we're a significantly better team when he's out there," manager Rocco Baldelli said.

Lewis is just one of dozens of first-year position players crushing it at the plate for contending teams, many of them with a postseason place clinched. By at least one key measure, this is the best class of rookie hitters the major leagues have ever seen.

Call this the year of the instant hit.

According to FanGraphs data, the advanced metric Wins Above Replacement total for all rookie hitters in 2023 (75.5) is the best since 1900, entering the final weekend of the regular season slightly ahead of the 2015 group (75.1) headlined by Kris Bryant, Francisco Lindor, Carlos Correa and others.

Corbin Carroll (Arizona Diamondbacks), Yainer Diaz (Houston Astros), Gunnar Henderson (Baltimore Orioles), and James Outman (Los Angeles Dodgers) are some of the most prominent and productive first-year standouts guaranteed more games in the postseason next month.

The 2023 rookies, who had a running start on the new rules regarding the pitch clock and pickoff limits in the minor leagues, have also blown away every other rookie class in modern major league history with their total - through Thursday - of 825 stolen bases. The next closest class (1977) had 691. Esteury Ruiz (Oakland Athletics) and Carroll each topped 50 steals.

Carroll, even by comparison to so many other dazzling debuts, is the clear front-runner for the National League Rookie of the Year award.

"He's an unbelievable talent, and he brings a certain edge to the game because of his precision and because of his athleticism, but he combines it all and goes out there and makes plays and does things and times it right," Diamondbacks manager Torey Lovullo said. "He's just gotten even better with the timing of everything that he does, and that's hard to do for a 22-year-old player. He can carry us."

Major league pitching in this rocket-armed era is as hard to hit as it's been in decades. So why are these rookies raking like they are these days? The 2022 class has the third-best WAR (54.9) of all time, according to FanGraphs, followed by 2019 (49.5).

"A lot of what we do at the major league level, process-wise, is more similar at the Triple-A level than ever before," Baldelli said. "We try to make it resemble what they are going to see when they get here. I think a lot of those small things add up to really help players in a big way."

That includes immersion in everything from pitcher scouting reports to advanced statistical data to video swing analysis.

"Hitting coaches in the minors are really good, and they communicate with the big-league hitting coaches as well," Diaz said through an Astros interpreter. "So it goes all the way down."

Lewis, who was recently sidelined by a hamstring strain, has a .921 on-base-plus-slugging percentage. That's the best in baseball this season for rookies with more than the 130 at-bats that disqualify them from that status for 2024.

The first overall pick in the 2017 draft likely would've been ready to join the Twins sometime in 2020 had there been a full schedule. The following winter, he tore his ACL during a workout. After more than a year of rehab, Lewis played 12 games for the Twins in 2022 before another ligament tear in the same knee.

Growing up in the Los Angeles area, he routinely faced strong pitching in high school, a trend that is not going to end anytime soon with the prevalence of one-sport specializing that puts teenage prospects in year-round training mode.

Another factor in accelerated development is major league teams inviting more prospects to spring training, exposing them earlier to elite pitching in exhibition games. Front offices also appear more willing to promote their rising stars faster through the farm system rather than subscribe to the old-school ethos of minor leaguers earning their stripes.

"When you perform, I think you should just go," Lewis said. "I think that's finally how they're going about it, and it's fun to watch all the young guys come up. At the same time, if I was a veteran, I would probably be saying, 'Hey, I think you should take your time.' But as a young guy now, it's fun to watch."

The Twins also leaned on significant contributions from rookies Edouard Julien and Matt Wallner to keep their lineup on track down the stretch while Correa hit well below expectation and fellow star Byron Buxton was again limited by injuries.

"They bring a lot of hits and really good energy," Baldelli said. "It's a hard thing to describe. But when you bring in new, vibrant guys, it's great for everyone. It pushes everyone a little bit when they are productive. It almost feels like a pick-me-up."

AP Baseball Writer David Brandt in Phoenix, AP Sports Writer Kristie Rieken in Houston and AP freelance writer Brian Hall in Minneapolis contributed.