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  • The Hidden Edge: How to Use Weather to Win MLB

The Effect of Rain on Player Performance

Jon Bales (JonBales)

Jonathan Bales is the founder of RotoAcademy and author of the Fantasy Sports for Smart People book series.

Rain rain go away,
Come again another day.

I had a friend who moved from our hometown (outside of Philly) to L.A., and he complained all the time about how he missed the rain and that the weather was “too nice” in California.

I think he’s out of his mind because rain is awful. Granted, I stay inside pretty much all day anyway, but I do sit by a window most of the time, so it ruins my entire work-and-watch-TV ambiance. How am I supposed to tackle a subject as exhilarating as how a light drizzle affects walk rates in Major League Baseball if it’s dark and gloomy outside?

I don’t like it to rain wherever I’m located, but from the months of April to October, I hope for as much precipitation as possible everywhere else in the country. I’m a huge advocate of utilizing the weather in daily fantasy baseball decisions and understanding how rain affects player projections is really, really important. Rain can also lead to a big edge, which is why I love it.

As you know, it’s extremely risky to roster pitchers who are in a game that could see rain. Even if the game doesn’t rain out, any sort of delay can be devastating to your lineup since starters almost always get pulled if they need to sit for any significant period of time. I might take a chance on a pitcher in a game with a small chance of rain in a tournament—although even that’s rare—but you simply can’t take unnecessary risks with your arms in cash games.

Batters are another story because they don’t get pulled if there’s a delay. Actually, a rain delay (or perhaps the precipitation itself) might actually help your bats. For one, the starter could get pulled early. Second, it could be the case that pitching itself is more challenging in the rain; I’m not a professional baseball player, but a wet baseball seems like it is more difficult to throw accurately than a dry one.

Stats in the Rain

Using Baseball Reference’s Batting Game Finder, I was able to examine every game played since 2000, which I broke up into three buckets: no precipitation, drizzle, and rain/showers. What’s considered a ‘drizzle’ and what’s considered an actual ‘shower’? I have no fucking idea, but let’s go with it.

Here’s a look at five different stats sorted by precipitation.

raweather

Stats in red are the ones that are best for hitters, while blue is the worst. You can see the only stat that improves for batters in games with no rain is HR/AB. That makes some sense since you’d think rain might knock down fly balls so that they don’t travel as far as they would otherwise. Still, those results are all similar: 0.27 HR/AB in rain, 0.28 in a drizzle fo’ shizzle, and 0.29 in clear skies. Basically no difference.

After HR/AB, however, every batter stat is best when a game has some form of rain—and the more rain, the better. Batters get on base 33.1 percent of the time in rain compared to 32.0 percent of the time in clear skies.

When I saw the OBP numbers, it made me think that perhaps a lot of this has to do with a lack of control from pitchers, which would be reflected in both walk and strikeout rates. And indeed, pitchers walk significantly more batters and strike out fewer in the rain.

With all of those numbers, it shouldn’t be surprising that teams have historically scored 3.6 percent more runs in games with rain than in those without any precipitation. The biggest effects are on walks and strikeouts: 9.6 percent more walks and 10.1 percent fewer strikeouts in rainy games.

That’s a big deal.

Using Precipitation to Your Advantage

I think that there’s a general misunderstanding of how to use the likelihood of precipitation to your advantage in daily fantasy baseball. A greater likelihood of rain—and thus more risk—isn’t always a negative.

While I wouldn’t roster a stack of hitters in my cash lineup if they’re in a game with a 70% chance of rain, I might do just that in tournaments to help separate from the pack. Users get scared off when there’s a high likelihood of rain, even in GPPs.

Although lots of games experience delays, not too many are actually postponed—certainly not enough to make up for sharp drops in usage that we see in games considered “high-risk.”

Rostering batters in games with a high likelihood of rain but a low probability of getting postponed is probably a really underrated tournament strategy. It’s something I like to do a lot, targeting high-upside offenses whose ownership will be down due to perceived risk. The reduced usage combined with the expected improvement in batting stats—due both to wet conditions and the potential for the starter to get pulled after a delay—combine to form the perfect storm (← You like that?) for daily fantasy baseball players.

And at this point, I think we need to change the old nursery rhyme.

Rain rain go away,
Just kidding stay around for a little while and force the opposing pitcher out of the game but don’t get out of hand because we need to get this game in I have the Blue Jays at five percent ownership.

I’ll be singing that one to my kids for years to come.

Rain rain go away,
Come again another day.

I had a friend who moved from our hometown (outside of Philly) to L.A., and he complained all the time about how he missed the rain and that the weather was “too nice” in California.

I think he’s out of his mind because rain is awful. Granted, I stay inside pretty much all day anyway, but I do sit by a window most of the time, so it ruins my entire work-and-watch-TV ambiance. How am I supposed to tackle a subject as exhilarating as how a light drizzle affects walk rates in Major League Baseball if it’s dark and gloomy outside?

I don’t like it to rain wherever I’m located, but from the months of April to October, I hope for as much precipitation as possible everywhere else in the country. I’m a huge advocate of utilizing the weather in daily fantasy baseball decisions and understanding how rain affects player projections is really, really important. Rain can also lead to a big edge, which is why I love it.

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About the Author

  • Jon Bales (JonBales)

  • Jonathan Bales is the founder of RotoAcademy and author of the Fantasy Sports for Smart People book series.