SkyKing162's Baseblog



A fan of the Yankees, Red Sox, and large sample sizes.


4.28.2004
 
WHEN HOMERUNS ARE HIT

Yesterday, John Lackey pitched a pretty good game, and hadn't surrendered any runs through 6 2/3 innings, at which point he was pulled in favor of Scot Shields after he loaded the bases. No problem, of course, since Brandon Inge was coming to the plate and Inge is one of the worst hitters in the American League (with apologies to Darin Erstad, Willie Harris, and quite a few others, actually). Of course, Inge proceeds to hit a grand slam, slamming Lackey with 3 ER. Still not a bad outing, and much better than Lackey's previous starts this year.

Tonight, Mulder hasn't been so hot, surrendering a bunch of hits and walks, before settling down and throwing a couple scoreless innings. He gave up a solo homerun to Jorge Posada, and was lucky Jorge didn't come to bat with men on base, like there had been most of the game. Mulder's outing would have been much worse had the HR come at a different time.

That got me thinking, are homeruns more likely to be hit at different game states? Most importantly, do more homeruns get hit without anyone on base? That makes a little sense - pitchers probably pay more attention to preventing homeruns when it will cost them more. Using Retrosheet data and ASS, here's a chart showing the probability of a homerun occuring at the different base states in the years 1972-1992 and 1999-2002:

basesit    hr      n        hr/n 

Loaded 2104 93587 .022
2nd & 3rd 1286 88385 .015
1st & 3rd 2801 139730 .020
1st & 2nd 5980 293575 .020
3rd 2202 125557 .018
2nd 6407 373843 .017
1st 16790 830747 .020
Empty 50073 2213779 .023


Here's just 1999-2002 data:

basesit    hr      n       hr/n 

Loaded 574 19657 .029
2nd & 3rd 357 17517 .020
1st & 3rd 680 26211 .026
1st & 2nd 1487 57621 .026
3rd 516 22648 .023
2nd 1535 69615 .022
1st 4115 153707 .027
Empty 12474 412260 .030


Looks like homeruns get hit more often with the bases empty, and not as much with runners in scoring position. Of course, once the bases get loaded, the rate increases again, probably because the pitcher has to throw strikes, or risk walking in a run. Of course, the reason might also be that the pitchers who allow a lot of baserunners are bad, and bad pitchers also give up homeruns.

What about if we consider the number of outs? Does the number of outs alone affect when homeruns get hit? Using 1999-2002 data:

outs  hr    n       hr/n 

2 6845 253370 .027
1 6992 259401 .027
0 7901 266465 .030


Hmm, a small advantage to the hitter with no outs. I don't know why, or if it's significant. I wonder if there are any unique combinations of base/out states that are extreme cases either for or against the hitting of homeruns:

outs:basesit hr     n      hr/n 

2 1st 1427 53555 .027
2 3rd 278 12337 .023
2 Loaded 254 9102 .028
2 1st & 2nd 609 25402 .024
2 2nd 681 30675 .022
2 1st & 3rd 320 12335 .026
2 Empty 3116 102140 .031
2 2nd & 3rd 160 7824 .020
1 2nd 553 24389 .023
1 1st & 3rd 236 9400 .025
1 Empty 3626 128661 .028
1 1st & 2nd 558 20669 .027
1 3rd 195 8133 .024
1 1st 1448 53731 .027
1 Loaded 240 7471 .032
1 2nd & 3rd 136 6947 .020
0 3rd 43 2178 .020
0 1st & 2nd 320 11550 .028
0 2nd 301 14551 .021
0 Loaded 80 3084 .026
0 1st 1240 46421 .027
0 1st & 3rd 124 4476 .028
0 Empty 5732 181459 .032
0 2nd & 3rd 61 2746 .022


Nothing crazy, but with no outs and the bases empty, homeruns occur at the highest rate. Those are the lead-off plate appearances (or plate appearances following lead-off homeruns), so maybe pitchers are just a little rusty or don't quite have their focus starting an inning.

If anyone's got any other explanations, let me know.


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