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Do pitchers get rattled after a long homerun?

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As I often do, I was thinking about baseball one day, specifically sluggers, and wondered if the act of ‘slugging' (hitting a ‘tape-measure' homerun) was any better than a run-of-the-mill homer.

I endeavored to study this. HitTracker was invaluable, as it measures the distance of every homerun hit; and BRef of course, because it compiles homerun logs for every player: the inning, the pitcher, etc.

So I looked at how pitchers fared after the tape-measure shots (termed ‘no-doubt') as compared to everything else (‘plenty' and ‘just enough' as determined by HitTracker). Would pitchers fare worse after a humiliating longball? Would there be any kind of ‘rattle effect'?

ERA and WHIP were the two stats I used to determine if pitchers improved or regressed after a homerun. I know they're not the end-all, be-all of pitching stats, but they're easy to figure out and are readily available in the game logs/box scores (as opposed to FIP or LD%).

Since I knew it would take many hours of research, I studied only three players, but was sure to take one each from a hitter's park, a neutral park and a pitcher's park. After all, if I only studied Mark Teixeira, he would have a greater percentage of ‘no-doubters' than most other hitters because Yankee Stadium is rather conducive to ‘no-doubters' (defined as: "the ball clears the fence by at least 20 vertical feet AND lands at least 50 feet past the fence"; so a 370 ft. shot to rightfield in Yankee Stadium may be a ‘no-doubter' yet a 380 ft. shot in Petco may not).

The three players were Mark Teixeira, Prince Fielder (from the neutral Miller Park) and Adrian Gonzalez (from the pitcher's paradise known as Petco Park). The study included all homeruns through July 20.

The number of ‘no-doubters' was directly linked to the ballpark: Tex had the most, followed by Fielder and then A-Gon. I didn't go purely by distance because I was more interested in any kind of ‘rattle effect' a homer that appeared long would have on a pitcher. A longball that gets out by plenty in rightfield can appear longer than a ball that just clears the centerfield fence.

There were 21 ‘no-doubters' hit by the three sluggers and 50 ‘normal' homers.

The results

After a ‘normal' homer was hit, pitchers pitched to a 4.53 ERA and 1.46 WHIP. And now for the surprise: after a ‘no-doubt' homer was hit, pitchers actually fared better: 4.15 ERA and 1.41 WHIP. That was the opposite conclusion I expected. The results are even more pronounced when measuring by distance: 4.28 ERA and 1.33 WHIP after 400 ft. (or longer) shots, 4.56 ERA and 1.56 WHIP after 399 ft. (or shorter) shots.

Now I know half a season's stats from three hitters isn't the biggest sample size, but I hope to increase the data field in the future and perhaps come to a more definitive conclusion. But still, it is intriguing and points to the possibility that pitchers bear down after a humiliating homer as opposed to getting rattled.

Other interesting tidbits

Pitchers were immediately pulled after 14% of ‘no-doubt' homers; on all other homers just 4% of the time. What value that has, I'm not sure.

For both types of homers (‘no-doubt' and all others), the average inning of occurrence was the same: two outs into the fifth inning (4.7). Perhaps that is the most frequent time at which starters begin to tire (though the data includes relief innings).

(The Excel file)