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Last year, eventual National League Rookie of the Year Paul Skenes made his major league debut on May 11 in what was the Pirates’ 40th game of the 2024 season.

In 2022, NL Rookie of the Year Michael Harris II didn’t debut until May 28. He played his first game in the Braves’ 47th game of the season.

That made me wonder how common it is for an eventual Rookie of the Year to be playing in the minor leagues in May—as Skenes was at this time last year—especially in light of what has turned out to be a weak NL rookie class so far this season.

Over the course of 78 seasons, a total of 156 players have won Rookie of the Year awards. When launched in 1947, only one overall ROY was awarded, but since 1949, an award has been given in both the American and National leagues. 

In two seasons in the 1970s, there were co-Rookies of the Year when two players tied for the vote lead.

Rookies Of The Year By Season Debut Month

Most Rookies of the Year make their season debuts in March or April, somewhere in the vicinity of Opening Day. This gives them the longest possible runway to make adjustments to MLB competition and build statistical volume to make the strongest ROY case. 

But as Skenes and Harris illustrate, Rookies of the Year are increasingly making their season debuts in May or later.  

Here is a look at how debut months for players who went on to win Rookie of the Year are distributed. Note that the data for the 2020 ROY race was excluded from the sample because of the strange nature of that season. The Covid pandemic reduced that season to 60 games and pushed Opening Day to July 23. 

83.8% March/April season debut (129 players)
13.0% May season debut (20 players)
2.6% June season debut (four players)
0.6% July season debut (one player)
0.0% August season debut
0.0% September/October season debut  

Recent Rookies Of The Year With Later Season Debut Dates

Skenes and Harris are part of a small but growing contingent of Rookies of the Year who not only did not make Opening Day rosters, but did not appear in a big league game prior to May 1.

Working from the present day backward, here are all the Rookies of the Year of the 21st Century who made their season debuts after April ended. As was the case above, the 2020 Rookies of the Year—Kyle Lewis and Devin Williams—are excluded. 

2024: Paul Skenes, RHP, Pirates (May 11)
2022: Michael Harris II, CF, Braves (May 28)
2019: Yordan Alvarez, LF, Astros (June 9)
2015: Carlos Correa, SS, Astros (June 8)
2014: Jacob deGrom, RHP, Mets (May 15)
2013: Wil Myers, RF, Rays (June 18)
2010: Buster Posey, C, Giants (May 29)
2009: Chris Coghlan, LF, Marlins (May 8)
2007: Ryan Braun, 3B, Brewers (May 25)
2005: Ryan Howard, 1B, Phillies (May 3) 
2004: Jason Bay, LF, Pirates (May 7)
2003: Dontrelle Willis, LHP, Marlins (May 9) 

Twelve of the 20 instances of ROYs who did not debut until May 1 or later occurred in the relatively small window between 2003 to 2024. In those 21 seasons, roughly every other year saw a ROY make a later-season debut. This could be tied to MLB clubs’ increasing attention to service time manipulation during this period.

Assigning a top rookie to Triple-A on Opening Day and keeping him there for about two weeks grants a club an extra year of contractual control. A player will now qualify for free agency after seven seasons rather than six. This effect might account for Rookie of the Year winners who debut in mid-to-late April.

Keeping a player in the minor leagues until mid-to-late June has a different type of financial implication down the road. The top 22% of players with less than three years of service but more than two qualify for arbitration a year early. These Super Twos are granted four trips through the salary-boosting mechanism of arbitration rather than the standard three. 

Service-time manipulation was the impetus for the players’ union negotiating the Prospect Promotion Incentive and pre-arb bonus pool into the 2022 Collective Bargaining Agreement with MLB.

How Important Is Previous MLB Experience?

A total of 80 Rookies of the Year—or 51% of the sample—had previous major league experience. In most cases, the player gained MLB experience in AL or NL play in the season preceding his rookie year. 

But 17 players appeared in an AL or NL game in multiple previous seasons prior to his ROY campaign. And in six cases—Jackie Robinson, Sam Jethroe, Willie Mays, Don Newcombe, Joe Black and Jim Gilliam—the player had prior experience in the Negro Leagues.

Latest Season Debut Dates For Rookies Of The Year

You may be wondering about the lone Rookie of the Year who did not debut until July.

That would be Hall of Fame first baseman Willie McCovey, the 1959 National League Rookie of the Year who did not debut until July 30—or 101 games into Giants’ seasons.

Here are the ROY winners who were called up the latest in the season, as measured by the highest total of team games already played. 

1. Willie McCovey, 1B, Giants (1959 NL)
Season debut: July 30. Age: 21. Team game: 101.

2. Wil Myers, RF, Rays (2013 AL)
Season debut: June 18. Age: 22. Team game: 70.

3. Yordan Alvarez, LF, Astros (2019 AL)
Season debut: June 9. Age: 21. Team game: 67.

4 (tie). Bob Horner, 3B, Braves (1978 NL)
Season debut: June 16. Age: 20. Team game: 59.

4 (tie). Carlos Correa, SS, Astros (2015 AL)
Season debut: June 8. Age: 20. Team game: 59.

6 (tie). Ryan Braun, 3B, Brewers (2007 NL)
Season debut: May 25. Age: 23. Team game: 48.

6 (tie). Buster Posey, C, Giants (2010 NL)
Season debut: May 29. Age: 23. Team game: 48

8. Michael Harris II, CF, Braves (2022 NL)
Season debut: May 28. Age: 21. Team game: 47.

9. Chris Chambliss, 1B, Indians (1971 AL)
Season debut: May 28. Age: 22. Team game: 43.

10 (tie). Jacob deGrom, RHP, Mets (2014 NL)
Season debut: May 15. Age: 25. Team game: 40.

10 (tie). Paul Skenes, RHP, Pirates (2024 NL)
Season debut: May 11. Age: 21. Team game: 40.

12. Dave Righetti, LHP, Yankees (1981 AL)
Season debut: May 23. Age: 22. Team game: 38.

13 (tie). Willie Mays, CF, Giants (1951 NL)
Season debut: May 25. Age: 20. Team game: 37.

13 (tie). Dontrelle Willis, LHP, Marlins (2003 NL)
Season debut: May 9. Age: 21. Team game: 37.

14. Don Schwall, RHP, Red Sox (1961 AL)
Season debut: May 21. Age: 25. Team game: 32.

15. David Justice, 1B/RF, Braves (1990 NL)
Season debut: May 16. Age: 24. Team game: 31.

In Summary

• An overwhelming number of Rookies of the Year—nearly 84%—make their season debuts in March or April.
• However, Rookie of the Year winners are debuting in May or June more frequently than they once did. Twelve of the 20 instances have occurred in the past 21 seasons.
• Prior major league experience is not a major factor in Rookie of the Year candidacy. A little more than half of winners—51%—had previous AL or NL experience.
• The Giants didn’t call up Willie McCovey until the 101st game of their season, by far the longest into a season that a Rookie of the Year was called upon.