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What A Year Off Might Do To Baseball Players’ Skills

Hundreds of professional baseball players may go months without participating in any games or practices organized by Major League Baseball clubs. The minor league season was canceled in June. Some major league players have decided to sit out the season because of COVID-19 concerns. And if there are more outbreaks, like the one involving the Miami Marlins, the major league season is at risk of being canceled all together.

For players not among the 60-man MLB rosters eligible to play and be coached on the field this season — and the vast majority of players in affiliated professional baseball are not on those rosters — it may be a “lost season of development.1

Mitch Horacek, a minor league pitcher for the Minnesota Twins who is not in the club’s 60-man pool, is concerned about what the cancellation of so many professional games means for baseball.

“Unfortunately, any way you cut it, baseball will be less talented next year in aggregate,” Horacek told FiveThirtyEight.

Could there be detrimental effects not only for players’ careers but for the overall quality of future play? The pandemic is unprecedented in many respects, but there was another time when a number of professional baseball players did not play games for non-injury reasons: World War II. With help from our friends at, we compared how major league players who missed at least one full season to WWII service performed before departing to European and Pacific theaters and after returning.2

We don’t have a huge sample to look at. There were 98 players who lost at least one full season to military service between 1939 and 1946. Of that group, there were 30 hitters to reach 150 plate appearances in their first year before service and also in their first season back. There were 15 pitchers to total at least 70 innings in their last year before WWII participation and in their first year playing after the war. All of those players returned in either the 1945, 1946 or 1947 MLB seasons. (There were 343 total MLB players who played in 1944 and 1945, so many returnees were facing players who did not miss time in previous seasons).

The hitters suffered some performance decline, relative to the league average. As a group, their OPS+ — which adjusts for the run-scoring environment and ballpark factors — declined by 5.2 percent, from an average of 118.1 pre-service to 111.9 in their first season back. But there were also cases like that of Ted Williams, who missed his age-24, 25 and 26 seasons and returned in 1946 to win the AL MVP award. Perhaps there was some aging effect in the group, but the average age of players in their return was 30.1 years, which likely placed near their prime performance years.

We get mostly the same results if we change our criteria slightly to get a bigger sample. Looking at the 37 players with at least 100 plate appearances, rather than 150, hitters’ performance slightly declined from a 111.4 OPS+ before WWII to a 107.2 mark in their return.

And if we look at all instances of one-plus seasons lost in service — adding one WWI case and eight Korean War veterans to our sample — there was only a slight performance dip (-0.9 percent).

Pitchers saw an even smaller effect.

Using ERA+, which also adjusts for stadium effects, the WWII veterans were 4.5 percent better upon their return. Take Bob Feller, who led the AL in wins in his last year before entering the war, but was better on a per-inning basis when he returned late in 1945. Looking at all pitchers in the group, they improved from a 108.2 ERA+ to a 114.3 mark.

When including all conflict-related cases — adding in one player who served in World War I and 10 Korean War veterans — the performance levels upon return were nearly flat. New York Yankees pitcher Whitey Ford returned after two years serving in the Korean War to go 18-6 with a 3.00 ERA.

So for those players that hope to return to affiliated games next year, perhaps they can take solace in the lack of dramatic decline in performance after military service. While World War II occurred more than 70 years ago, changes to technology and training practices have perhaps allowed game play to be less important to development today. After all, many modern career breakthroughs have occurred far from organized baseball fields. Yankees pitcher Adam Ottavino turned around his career thanks to a new pitch and better command honed in the confines of a Manhattan storefront. Los Angeles Dodgers third baseman Justin Turner and Boston Red Sox slugger J.D. Martinez rebuilt their swings and careers in various Los Angeles-area batting cages, morphing from bench players into stars. Indeed, some players are getting creative in the face of the pandemic.

Teams are, too. The Baltimore Orioles’ new leadership team is attempting to take advantage of the pause as best they can. Player development director Matt Blood has spent scores of hours with players on Zoom video calls this year. The video chats have focused on areas like mindfulness and nutrition. “Zoom dinners,” as Blood calls them, have pushed players to avoid relying on fast food. “We all cook the same meal, at the same time, so that we learn, and part of it is also so we can be together and see each other’s faces,” he said. The Orioles’ strength and conditioning staff helped players construct improvised weight-training equipment for those with limited means or without access to gyms, he added.

Of course, a major issue with players trying to develop away from their organizations is the lack of uniform access to facilities, tools and coaches.

Horacek said the Twins are in regular contact with their players but that there is no “set protocol” to follow. “I think they realize that they can’t ask too much of us because of the obstacles we face in training,” Horacek told FiveThirtyEight. “Many guys I know are just doing whatever they can, which certainly isn’t enough to develop.”

Even if clubs keep paying minor leaguers their paltry salaries, Horacek says players are looking for backup plans with so little future assurance of work — baseball has proposed reducing the affiliated minor leagues by 42 clubs next season. Horacek has started a web-development business that designs tools for teams and companies in the baseball business.

“I have a buddy who replied to his [organization’s] texts asking what he’s planning to do to ‘stay ready’ [by] saying ‘I’m not doing a goddamn thing for you guys anymore,’” Horacek wrote. “I think most players will shut it down until next year. Many will retire …. Some players might take this time to develop in the gym, but only those with the means to do that will be able.”

So perhaps the key question is not how players will develop without games, but how many will return at all.


  1. The Opening Day major league rosters included 30 active players, shrinking to 28 players two weeks after the first game and to 26 players another two weeks after that. The other players will train at an alternate facility separate from each club’s home park. The pool includes all players on each club’s 40-man roster that teams “anticipate participating” this season, with the rest typically composed of clubs’ best prospects, like Tampa Bay’s 19-year-old shortstop Wander Franco, or minor leaguers who clubs believe can fill immediate needs.

  2. There were 11 additional players who lost a full year or more of their careers to other military conflicts. While the data is limited to major league players, the effect of missing time to non-injury is likely to be similar across professional levels of baseball as the number of games and structures of seasons are similar (and minor leaguers would not be adversely affected by aging curves).

Travis Sawchik is a former sportswriter for FiveThirtyEight.