Looking Back on Another Remarkable Rookie Class

The 2023 season gave us the most predictable pair of Rookie of the Year races in recent memory. Gunnar Henderson and Corbin Carroll were our top two prospects entering the year and the overwhelming preseason ROY favorites among our staff. At season’s end, they each earned all 30 votes on their respective ballots. It was only the second time in the 21st century that both the AL and NL ROY winners were unanimous decisions (Aaron Judge and Cody Bellinger won unanimously in 2017) and the first time that the clear preseason favorites were also the undisputed victors. By comparison, the 2024 Rookie of the Year races were about as predictable as a toddler’s favorite food.

You don’t want Wyatt Langford? But you loved Wyatt Langford yesterday!

How about Jackson Holli… No, I’m sorry, please stop crying, we can send Jackson Holliday back to Triple-A!

So you either like Paul Skenes or Jackson Merrill, but you won’t tell me which one and if I pick wrong you’ll throw him on the floor and scream? Got it.

AL Rookie of the Year Luis Gil missed most of the 2022 and 2023 seasons recovering from Tommy John surgery. Even before he tore his UCL, a future move to the bullpen seemed possible, and if it weren’t for his strong spring training (15 2/3 IP, 2.87 ERA) and Gerrit Cole’s elbow injury, that’s likely where Gil would have begun the 2024 campaign. Runner-up Colton Cowser was a slightly more promising prospect; he graduated with a 45+ FV to Gil’s 40+. Still, like Gil, his starting role in the majors was not guaranteed until he earned it with a red-hot spring and an equally scorching start to the regular season.

Of the three finalists in the AL, only third-place finisher Austin Wells ranked among our top 100 prospects ahead of the season. And of the five players who earned votes for AL Rookie of the Year as part of our preseason staff predictions exercise (Langford, Evan Carter, Junior Caminero, Holliday, and Colt Keith), only Langford ended up earning so much as a single vote from the BBWAA. He finished seventh with one second-place vote and four third-place selections.

The NL contenders weren’t quite as surprising. All three finalists, Skenes, Merill, and Jackson Chourio, were among our top 30 prospects entering the season. Meanwhile, Yoshinobu Yamamoto, the most popular NL Rookie of the Year choice in March, only fell out of the race due to a triceps injury that cost him almost half the season. Yet, although the NL field was not so surprising, at least not like the AL field turned out to be, the final results were just as hard to predict. The voting ultimately wasn’t all that close – Skenes earned 23 first-place votes to Merrill’s seven – but those numbers might undersell what a difficult decision all 30 voters had to make. Dan Szymborski did a great job breaking down why it was such a tough choice (and why he ultimately cast his ballot for Merrill).

Merill showed off all five tools in 2024, the most impressive of which was his center field defense, considering he was a shortstop up until this year. OAA, UZR, and Baseball Prospectus’s DRP loved him in center. Only DRS disagreed (0 DRS), but even a perfectly neutral defensive performance is admirable coming from a 21-year-old playing the position for the first time. Combine that glove with good baserunning, great contact skills, and a surprising amount of power, and you get Merill’s 5.3 WAR, more than a full run higher than any other rookie in either league. The last rookie to produce more WAR and still lose the ROY was Kenny Lofton (5.8 WAR) in 1992. Thus, the fact that Skenes came out on top is a testament to the dominant season he put together. Over 23 starts and 133 innings, he pitched to a 1.96 ERA and 4.3 WAR. No rookie starter has thrown more innings with a lower ERA in over 50 years. If Skenes had been on the Pirates’ roster on Opening Day, it’s very likely he’d have surpassed Merrill’s 5.3 WAR, and this conversation wouldn’t have been so complicated. But that’s the debate in a nutshell. On the one hand, you can’t blame Skenes for not pitching in the majors sooner. He was clearly ready to make the Pirates’ roster out of camp. On the other hand, you can’t give him credit for innings he didn’t pitch.

Only two more rookies earned votes in the NL, and either of them very well could have won the award outright if they’d played in the opposite league. Chourio wasn’t quite as strong of a hitter as Merrill, but he excelled on both sides of the ball, finishing with 21 homers, 22 steals, 6 OAA, and 3.9 WAR. Meanwhile, fourth-place finisher Shota Imanaga was terrific in the first year of what now looks like an incredibly team-friendly four-year, $53 million deal with the Cubs. His 2.91 ERA ranked third among all qualified NL pitchers. His 3.72 FIP was significantly higher, so his 3.0 WAR ranked just 19th among NL hurlers. Still, among rookie pitchers, it was second only to Skenes.

A trio of NL infielders also deserve some recognition for their strong rookie seasons; any of them might have earned some down-ballot votes in a weaker year. Masyn Winn (3.6 WAR) and Joey Ortiz (3.1 WAR) were strong defenders with roughly league-average bats, while Tyler Fitzgerald (3.0 WAR) put up a .217 ISO and 132 wRC+ over 96 games while looking just capable enough with the glove to be an everyday shortstop.

The AL rookie class didn’t have quite as much top-end talent or mid-tier depth. Gil was a solid, mid-rotation starter who moderately outperformed his peripherals. That’s no knock on the righty, who was a valuable member of the Yankees’ AL pennant-winning roster, but he didn’t have a star-making debut season like Skenes, Imanaga, or Yamamoto. According to WAR (and 14 out of 30 voters), Cowser actually had the more impressive season. Even so, it’s hard to ignore how similar Cowser’s numbers were to those of the NL’s distant third-place finisher Chourio. And considering neither Gil nor Cowser was a slam dunk to win, one might have thought Wells would earn some first-place votes himself. He blossomed into a terrific defensive catcher by anyone’s metrics (13 FRV, 11 DRS, 14.5 DRP), which is quite the accomplishment. Unfortunately, he disappeared at the plate in September (22 wRC+) and may have cost himself the hardware in the process.

Where the AL rookie class really stood out this year was in the bullpen. Two of the top three relievers by WAR were AL rookies: Cade Smith (2.7 WAR) and Mason Miller (2.3 WAR). Miller was the bigger story because of his triple-digit fastball velocity, gaudy strikeout totals, and strong start to the season, but Smith ended up with a lower ERA and FIP in 11 1/3 additional innings. Nonetheless, narrative often prevails in awards voting, and Miller finished ever so slightly ahead of Smith. It probably didn’t help Smith’s case that he was hidden behind Cy Young finalist Emmanuel Clase in the Guardians’ bullpen, whereas Miller racked up 28 saves as the A’s closer.

The other two AL rookies receiving votes were outfielders Wilyer Abreu (3.1 WAR) and Langford (2.9 WAR). The two had similarly valuable seasons; each was above average at the plate, while Abreu was the stronger fielder and Langford the better baserunner. However, Abreu came into the season as a relatively unheralded name, and Langford’s top-prospect reputation preceded him. Thus, compared to Abreu, who looked like a blossoming star, Langford almost seemed to be a disappointment — at least relative to expectations. That could explain why Abreu earned a couple more votes, including a pair of second-place selections from outside the Boston chapter of the BBWAA.

The emergence of star prospects like Skenes and Merrill, the breakouts of less-heralded rookies like Cowser and Gil, and the close ROY races in both leagues highlight what was another banner year for rookies. Overall, they combined for 138.3 WAR in 2024, surpassing the previous record of 134.8 set by last year’s rookie class:

What’s more, this past year’s rookies represented 13.8% of WAR league-wide. That figure isn’t quite record-breaking, but it is the highest percentage of WAR to come from rookies since 1947, fittingly the first season of the ROY award, created for and won by Jackie Robinson. These are the top seasons in history according to percentage of WAR produced by rookies, excluding 1871 (when everyone was a rookie):

Of course, all of this is partly because rookies have seen a steady increase in playing time since the start of the 21st century. When rookies play more, it stands to reason that they’re going to produce more value. Therefore, it’s also relevant to look at the ratio of rookie WAR to rookie playing time, which I’ve calculated by taking the percentage of league-wide WAR produced by rookies and dividing it by the percentage of league-wide plate appearances and batters faced by rookies. Rarely is that ratio going to be higher than 100% (that would mean rookies were outproducing non-rookies on a rate basis), but the closer the number is to 100%, the better rookies have performed compared to the rest of the league.

By this metric, the 2024 season isn’t quite as historic. Still, it was the strongest year for rookies since 2012 and one of the top three seasons of the last 30 years. The graph begins in 1916, when TBF data is first available:

Another metric to consider is the number of rookies who reached a certain WAR threshold. Decimal places of WAR are pretty insignificant, and any WAR threshold I pick is going to be somewhat arbitrary. Still, I think it’s interesting to identify the number of rookies who made a lasting impression in any given season. For instance, 28 players on our rookie leaderboards finished with at least 2.0 WAR this past season. The last time there were more two-win rookies was 1920, which was the first season that any of the Negro Leagues are considered major leagues, and therefore the rookie season of all-time great players like Oscar Charleston and Cristóbal Torriente. Meanwhile, the last time rookies made up such a high percentage of all two-win major leaguers was 1947:

Similarly, the last time there were more three-win rookies on our leaderboards was 1920, and the last time rookies made up a higher percentage of three-win players was 1947.

At this point, I feel compelled to note that due to MLB’s two-pronged rookie eligibility requirements, our leaderboards include a handful of players who have already exhausted rookie status. It’s easy to filter out players who have reached 130 at-bats or 50 innings pitched in the majors; it’s harder to filter out those who have accumulated 45 days on an active major league roster during the championship season (not counting days on the injured list) without reaching either of those other playing time thresholds. For the sake of consistency, the numbers I’ve cited up to this point come directly from our leaderboards. I could have manually extracted the few players who weren’t technically rookies in 2024, but it would be impossible to do that for every season on record. Moreover, I don’t think it’s a grave sin to include a player like Lawrence Butler when I’m looking at general rookie trends; if he had been called up just a week later in 2023, he’d still have been rookie eligible in 2024.

However, in case that makes you skeptical about the greatness of this year’s rookie class, let me ease your troubled mind. Even if I manually correct the 2024 data and remove players like Butler, rookies still made up a higher percentage of all two-win players in 2024 than in any season since 1920 and a higher percentage of all three-win players than in any season since 1984. And keep in mind, that’s without manually correcting the data in any other season.

Some of these rookies will become superstars in the years to come. At least one of them already is. Others may look back on 2024 as the best year of their careers. As their futures unfold in different ways, we may soon forget that all of these players crossed the major league threshold in the same season. Still, for this brief moment in time, all of these players are a unified graduating class. So, let me leave them with the distinctive, touching, and unforgettable words of my high school principal’s graduation speech: “Today is the first day of the rest of your lives.”