Five Notable Players Who Have Opened 2024 in a Sophomore Slump

Five budding MLB stars, who have failed to meet the lofty expectations they set from themselves after stellar rookie campaigns in 2023.

PHOENIX, ARIZONA - MAY 19: Corbin Carroll #7 of the Arizona Diamondbacks gets ready in the batters box against the Detroit Tigers at Chase Field on May 19, 2024 in Phoenix, Arizona. (Photo by Norm Hall/Getty Images)

They were MLB rookies who made big headlines in 2023: Corbin Carroll, Yanier Díaz, Eduard Julien, Nolan Jones, and James Outman. The question was whether they could avoid that infamous “sophomore slump” in 2024.

Whether the sophomore slump is a real thing remains a subject of debate. Often, opposing teams get better at coming up with strategies that knock a young player off his game, and adjusting can take time; sometimes, a young player may try to make improvements that don’t really work — or at least not early in the season. After all, baseball is a game of adjustments.

So far, five of 2023’s most impressive rookies are struggling through their second season. The talent is there, as evidenced by their rookie season, but right now, the pieces aren’t coming together. What happened? Here are five position players still trying to find a way back to their rookie glory.

Corbin Carroll (2023 NL Rookie of the Year)

  • 2023 numbers: .285/.362/.506; 133 wRC+; 54 SB; 25 HR; 5.4 fWAR
  • 2024 numbers: .191/.281/.272; 63 wRC+; 8 SB; 2 HR; -0.2 fWAR

Just a few months ago, Corbin Carroll was the unanimous choice for NL Rookie of the Year in addition to landing fifth in the NL Most Valuable Player voting. Given where Carroll is now — struggling to get on base — it can be difficult to recall that electric rookie hitting all those homers and stealing all those bases.

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What happened?

Clearly, Carroll got off to a slow start. As Jordan Shusterman explains, the speed with which Carroll moved through the Arizona Diamondbacks system coupled with a stellar rookie campaign ultimately affected his development:

Early on this season, the inclination from Carroll and Arizona’s coaches was to let him “ride it out” because of what he showed last year. “He moved so fast through the system, he never really had the opportunity to try some different stuff and see what it means to work through something, especially in-season,” D-backs hitting coach Joe Mather told Yahoo Sports. But eventually, it became apparent that some intervention was required.

Since then, Carroll has been working with the D-backs coaches to make swing adjustments — something notoriously difficult to do during the season. Additionally, Carroll had improved his swing metrics over the course of the offseason to the overall detriment of his its effectiveness. (Read a detailed analysis here.)

There are questions, too, if Carroll’s nagging shoulder issues have returned though he asserts that is not the case. Still, for a D-backs team desperate to get back on track, they eagerly await the return of 2023 Corbin Carroll.

Yainer Diaz

  • 2023 numbers: .282/.308/.538; 127 wRC+; 23 HR
  • 2024 numbers: .259/.294/.373; 90 wRC+; 3 HR

Yainer Diaz was one of the biggest breakouts of 2023. The Houston Astros catcher showed elite power from the catcher position hitting 23 home runs and 22 doubles in just 104 games.

This year, Diaz is not driving the ball with the same authority, as his HardHit% has dropped and he is hitting the ball into the ground 55.6% of the time, which gives him the fourth-highest ground-out percentage in baseball.

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Last year, Diaz had a 43.2% groundball rate. We are seeing a drop in fly balls and line drives off of Diaz’s bat, which has taken away from his extra-base power. Exacerbating the problem is a low Barrel% — 5.6% so far in 2024 compared to 12.2% in 2023.

Diaz’s slump is not as pronounced as Carroll’s is. And he’ll need to get back to barreling the ball as he did in 2023 and hitting it in the air. He’s been effective in handling the Astros pitching staff. Now he just need to get things working on the offensive side of the plate.

Edouard Julien (2023 AL Rookie of the Year Finalist)

  • 2023 numbers: .263/.381/.459; 136 wRC+; 16 HR; 2.8 fWAR
  • 2024 numbers: .210/.315/.399; 108 wRC+; 7 HR; 1.0 fWAR

What a year 2023 was for Edouard Julien, who was called up and over the course of 109 games hit 16 homers (136 wRC+). Add to that the lowest chase rate in MLB (17.2%) and a 15.7% walk rate.

Not bad!

He’s still off to a good start in 2024, but the numbers are not as impressive as they were last year. What happened?

Matthew Trueblood argues that he’s become “too passive” at the plate. He’s simply not swinging enough. Meanwhile, Ted Schwerzler makes a case that in addition to that, Julien is trying to hit for a power in a way that is incompatible with the part of his game that works well.

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To be clear, Julien is still an above-average player, but it’s a comedown from his 2023 season.

Nolan Jones (2023 NL Rookie of the Year Finalist)

  • 2023 numbers: .297/.389/.542; 135 wRC+; 20 SB; 29 HR; 3/6 fWAR
  • 2024 numbers: .111/.273/.111; 15 wRC+; 2 SB; 1 HR; -0.6 fWAR

Nolan Jones is an admitted “slow starter,” who when he had another terrible Spring Training, most just assumed it would pass when the weather warmed up. After all, he left Scottsdale slashing .250/.310/.385. Although he had yet to hit a home run, he’d managed five doubles and a triple.

The expectations were he would continue to progress. That has not happened.

Jones’ strikeouts are up — 35.9% K% compared to 29.7% in 2023. Moreover, he is unable to hit the ball with any kind of authority — a 3.5% Barrel% compared to 15.7% in 2023. He also struggling with a nagging back issue over the last month that ultimately led to a stay on the IL. (Read a more detailed analysis of the issues here.)

Currently, Jones is on a rehab assignment with the Albuquerque Isotopes, but suffered a knee injury there:

It’s bad news for a very bad Rockies team that desperately need a healthy Jones back in the lineup.

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James Outman (2023 NL Rookie of the Year Finalist)

  • 2023 numbers: .248/.353/.437; 118 wRC+; 16 SB; 23 HR; 4.0 fWAR
  • 2024 numbers: .147/.250/.266; 56 wRC+; 2 SB; 3 HR; -0.1 fWAR

Even though he has been the Los Angeles Dodgers’ starting center fielder in 2023 and 2024, James Outman was sent to Triple-A Oklahoma City last weekend.

Outman’s slump was deep given a 56 wRC+ with only three home runs and 10 RBI after appearing in 36 games this season. When comparing it to his 2023 numbers, the difference is clear.

It was part of a series of roster moves the Dodgers made, and manager Dave Roberts was diplomatic: “It was a tough one. . . . I don’t think any of us expected to be in this position given last year and our expectation for him this season. We felt that James needed an opportunity to go down and play every day. There’s something to getting out of this environment.”

Outman is, simply, not hitting. Giving him a change of scenery makes sense, and given the Dodgers’ stellar development system, his odds of returning to the MLB roster are good.

Are All Sophomores Slumping?

The sophomore slump is not some self-fulfilling prophecy. Elly De La Cruz, Gunnar Henderson, Anthony Volpe, and Jordan Westberg are evidence of that, as all those players have either met last year’s production or have far exceeded it.

Slumps are natural in this sport, regardless of the age of the player or their MLB experience. The difference with sophomores is that their slumps can be more pronounced because they have never experienced them, especially at the big league level if they are coming off stellar rookie seasons.

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Look at the list of the five names above who have excelled this year. All of them endured struggles during their rookie seasons that they grew from and came back this year better players.

Anthony Volpe has already met his 2023 fWAR production of 2.0 wins above replacement across just 49 games played. Last year it took 159 games to reach an fWAR of 2.0.

Elly De La Cruz has almost lapped himself in stolen bases from last year, needing just 48 games to swipe 30 bases because he is getting on base at a much better clip than last season, when he stole 35 bags in 98 games.

Gunnar Henderson was pretty darn good in his AL Rookie of the Year campaign in 2023, but he also endured struggles in the first half before breaking out and running away with the award down the stretch. Henderson has built off that, and is now an MVP candidate.

Meanwhile his teammate Jordan Westburg has gone from being about a league average hitter in 2023 (97 wRC+) to hitting .288/.339/.509, with a 141 wRC+ in 2024.

Consistency is very hard to find in baseball, particularly at the highest level. Players can boom or bust at any time, at a far more ramped pace than we might see in other sports. When you try to evaluate a young player, the lack of a track record always leaves doubt into what they will eventually become.

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There is every chance that the five second-year players who are off to a slow starts this year come alive down the stretch and remind us of the players they were during their rookie seasons. For now though, they will have to continue to make adjustments until they can rediscover that success.