Does Sending Players to the WBC Screw Teams Up?

On Sunday afternoon, a friend of mine was straight up not having a good time watching his favorite baseball team. The Phillies, defending NL champions and consensus favorites to return to the playoffs this year, were losing to the Rockies. They’d already done that once this weekend and are heading into the last week of April under .500. So he came up with an interesting theory: With so many players leaving Phillies camp to play in the World Baseball Classic, perhaps the interruption in spring training had a deleterious effect on the team’s preparation and/or chemistry.

Then he asked me if I knew of anyone who’d studied the issue. I said no and almost let the matter drop right there. Looking at the statistical leaderboards, playing in the WBC didn’t throw Shohei Ohtani off his schwerve. (Or Ronald Acuña Jr., or Randy Arozarena, or Xander Bogaerts)

Most of all, there are more direct explanations for the Phillies’ slow start: Bryce Harper is hurt, they’re down to something like their fourth-string first baseman, and there’s a specific Phillies fan who’s done something to anger the baseball gods and call down their wrath. His name is Nick, he lives in Christiana, Delaware, and the baseball gods will not relent until he is found and sacrificed upon a stone altar. Hurry, there’s no time to lose.

Keen observers will look at the scoreboard from Sunday and realize that the Phillies went on to win the game my friend was freaking out about by a score of 9–3, and the Phillies are 3 1/2 games out of a playoff spot with more than five months’ worth of season left. Obviously they’d rather be 3 1/2 games up, but with Harper and Ranger Suárez nearing game-readiness, it’s not the end of the world. Nevertheless, I decided to look into the issue, mostly because when my friend brought the idea to me, it was almost 2 p.m. and I had absolutely no idea what I was going to write about for Monday.

But at this point in the season, everyone’s looking desperately for any explanation for a team’s perceived underperformance. There’s probably an extent to which Phillies fans are just Like This, but they’re not unique. Other friends of mine who follow the Dodgers, Cardinals, Mariners, Giants, Angels, and White Sox (okay, the White Sox do seem to be in real trouble) are grinding their teeth down to the roots from anxiety. Unless you root for the Rays or the Pirates, you’ve probably got some gripe with your baseball team right now.

So just for fun, let’s investigate this specific claim. Does having players in the WBC slow a team down at the start of the regular season?

First, I went through a list of MLB-affiliated players who appeared on WBC rosters, more than 300 in all, and eliminated late injury scratches and players who only appeared in a country’s designated player pool. From there, I narrowed the list to the 156 players who participated in the WBC and have either appeared in a major league game this season or are currently on the major league injured list.

There are two ways to look at this information: qualitatively and quantitatively. And for the teams at both extreme ends of the WBC participation spectrum, there are narratives to be had if you want them badly enough.

The Astros had 12 players participate in the WBC, most of any team. Not only did they lose Jose Altuve, who broke his thumb in Venezuela’s quarterfinal loss to the United States, but they also started slow, losing 12 of their first 20 games before a four-game winning streak brought them back above .500 and within striking range of the Rangers.

The Cardinals had 11 players go to the WBC, including seven whose teams made it to the semifinal. St. Louis has probably been the most disappointing team among the preseason contenders, with a 9–13 start, and its WBC contingent has been all over the place. Tommy Edman and Paul Goldschmidt have been good, Miles Mikolas bad, Nolan Arenado somewhere between the two. Plus Adam Wainwright, Lars Nootbaar, and Giovanny Gallegos have all been hurt this season.

The Rangers, by contrast, only had one major league player at the WBC. They’ve been one of the biggest positive surprises of the season so far.

But for a compelling case study, you need a causal mechanism, and I’m not sure what that is. Injuries, like the ones suffered by Altuve or Edwin Díaz, are one thing. But WBC participants have their workloads monitored, often to an extent that frustrated fans of the tournament. Perhaps returning to the start of the MLB season is a letdown after the high of a deep international tournament run? But Ohtani, Arozarena, and even Mike Trout are powerful counterexamples here. Does interrupting spring training screw with team chemistry somehow? Maybe, but every player who went to the WBC had been in big league camp for three weeks already, and many of them had played with these teammates before.

What do the numbers say, then?

Well, the first thing to do is find a way to measure team performance. Raw winning percentage is problematic, because, as you might expect, good teams tend to have more players picked for international duty. Seven of the 10 teams that sent seven or more players to the WBC made the playoffs last season.

So I decided to measure each team against its preseason expectations; specifically, I compared their preseason playoff odds and projected winning percentage to those figures after Sunday’s games. Here’s how the 10 teams with the most WBC players are doing.

Not awesome, it turns out. Eight of them have lost ground in the playoff race, four by more than 17 percentage points, though it’s also worth pointing out that the biggest mover by far, in either direction by both winning percentage and playoff odds, are the Rays. And Tampa Bay sent seven players the WBC, including six position players. Of those, Isaac Paredes is the only one with an OPS under .900 at the moment. If there’s a WBC curse, it does not apply in Pinellas County.

Empirically, there isn’t a correlation between WBC participation and team performance, at least not one worth exploring. In statistics, the R-squared value measures correlation between two variables, expressed as a value between 0 and 1. In social science, anything above 0.5 means you’re on to something; anything below 0.1 means you should throw your regression in the trash and go home. The R-squared for number of participants against change in winning percentage is 0.0065.

For number of participants against change in playoff odds, the correlation is much stronger: 0.0399.

It’s always nice to get a visit from the null hypothesis.

What a relief. As a hardcore pro-WBC partisan, I would’ve been most distressed to find any evidence that sending players screws up a team’s mojo. As it stands, feel free to freak out as much as you like about your team’s early-season performance. Just know that the WBC probably isn’t to blame.