Are World Baseball Classic Players Actually Underperforming in 2026?

Approaching the end of a 2026 season that didn’t match his stratospheric standards, Paul Skenes attributed some of his problems this year with velocity to his participation in the World Baseball Classic.

Usually, that time of year, you’re kind of ramping up and it’s a little bit slow. You can kind of get onto the slope and find your body. One live [batting practice], you’re topping at 97 [mph], and then the next you’re 98, 99. And that wasn’t the case this year. Looking back, I don’t think that really helped.

This notion from Skenes did not come out of nowhere. A wide assortment of people has addressed this question on some level. Our very own Michael Baumann touched on it in 2023, though he was looking more at teams as a whole than players.

I’m a natural skeptic when it comes to claims of causation, which tend to be fueled by anecdote. From the supposed sophomore slump to the suspected swing-ruining impact of the Home Run Derby, there’s a lot of loosey-goosey if-then statements going around. But as these things go, the theory that WBC participation in a given year negatively affects player performance in the corresponding campaign has a lot of plausibility. The WBC is a very different environment than typical spring training games, and it comes at a time when players are normally focused on getting ready for the regular season. It doesn’t sound crazy to think these changes in preparation have some kind of deleterious effect on a player. However, we should test these things.

To do this, I collected a sample of all the players who have registered either 200 plate appearances or 40 innings pitched in the majors this season, and then separated them into two buckets: those who played in the 2026 WBC and those who didn’t. From there, I examined how their actual performance compares to their final ZiPS projections entering the season.

As of Thursday morning, 81 of the 357 position players who’ve recorded at least 200 plate appearances this season participated in the WBC. These players run the gamut from Pete Crow-Armstrong, who has exceeded his ZiPS-projected wRC+ by 45 points, to Jarren Duran, who has underperfomed his projection by 47 points.

The average WBC hitter underperformed his wRC+ projection by 3.8 points, with a median right around the same number (3.9). This is a smaller underperformance than it sounds, because if you look at the control group, the players who didn’t play in the WBC underperformed their wRC+ projections by an average of 2.4 points, with a median of 2.9 points. If you also use minor league translations to more accurately capture underperformers who were demoted to the minors, the average underperformance for the WBC participants drops to 4.7 points of wRC+, and the non-WBC player underperformance declines by a similar margin, to 4.0 points. Comparing these results to those of the 2023 WBC participants gives us a similar statistical conclusion: The negative impact of playing in the WBC, if it’s real at all, appears to be exceedingly small.

Of course, we’ve only analyzed position players so far. It’s certainly a possibility that a huge change in routine affects pitchers differently than hitters. Our study includes the 382 pitchers who’ve pitched at least 40 innings this season, 59 of whom participated in the WBC. I’m also going to look at year-over-year fastball velocity change, to directly test what Skenes was talking about. I’m using ERA- instead of ERA+ because the weirdness of extreme values of ERA+ tends to distort things.

As a group, the WBC pitchers outperformed their preseason projections by about 4 points of ERA- (-4.2 points vs. projection). The non-WBC pitchers outperformed by a similar margin, at -3.8 points of ERA- vs. the preseason projections. As before, the conclusion doesn’t change if you look at 2026 minor league translations or repeat the exercise with the 2023 WBC pitchers.

For velocity, I gathered a sample of all pitchers who threw 10 innings in both 2025 and 2026, and I specifically looked at the velocity of the fastest pitch type in their repertoire. The average WBC pitcher improved his velocity by 0.03 mph from 2025 to 2026. The average non-WBC pitcher saw his velocity go up by 0.04 mph.

So, what does this mean? At least from the data we have, there’s little reason to believe that playing in the World Baseball Classic has a negative effect on a player’s regular-season performance, as a general rule*. This is a good thing for baseball, as the WBC is a great showcase of the game to an international audience, and I hope that it continues to spread baseball to countries not known traditionally for being into the sport.

Note there’s an asterisk in that last paragraph, and it’s an important one. This is an examination of the effect on a macro level. Humans are complex animals, and it’s very possible that there are some players who may see a negative effect from replacing their low-key spring training with an international tournament. For that reason, players should think long and hard about how their participating might affect their regular-season preparation. Still, this study should provide some encouragement for players who want to compete in the WBC, and some reassurance for teams and fans who would otherwise be concerned.