June 29, 2017

Judicial Watch

I was watching the Yankees game against the White Sox Wednesday night with some casual baseball fans. They had not seen Aaron Judge hit before. When they saw him hit his 27th home run, they were impressed with the apparent ease of the swing. Judge seems to just swat the ball and it goes out.

Since he continues to be on a HR tear, and because it’s about half-way through the season, I started tracking his probability of setting the AL record for home runs in a season. While a number of NL hitters beat Roger Maris‘s mark of 61 home runs in a season, no AL hitter removed Maris from the league record. The spreadsheet tracking Aaron Judge’s HR progress is here.

I had to decide on an intrinsic HR probability for Judge (HR/Plate Appearance). His current career number is likely too high. Plenty of rookies play great in the first half, then fizzle in the second half. Mark McGwire is a great example. So I took Judge’s career rate from a few days ago and did a 50/50 regression to the league rate, and came up with 0.0534. That puts Judge’s current probability of breaking Maris’s record at .00072, or about 1 in 1400. That’s a good, conservative estimate. We’ll see how well that number bears out over the season.

In regards to the RBI race, the simulator now has Judge beating or tying Nelson Cruz 88.7% of the time.

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