Homerun kills rally, film at 11

File under “Stupid things that sportscasters say.”  This one only happens once in a while, but it does happen.  A team is behind by 5 or 6 runs late in a game, but strings a couple of hits together and pulls to within 3 or 4 with a runner still on.  I’ve seen this happen a few times and the Joe Morgans of the world always seem to say the same thing.  “You don’t want to hit a home run here, because a homerun will kill the rally.” 
I suppose the rallying team would rather appreciate some sort of base hit or walk or hit batsman or catcher’s interference, but why not a home run?  After all, a home run is the single most advantageous hit there is.  It makes sure that everyone on base scores, as well as the batter.  A double generally scores the runner s on second and third, but isn’t a guarantee for the runner on first and the batter is only half way to his goal.  Will someone tell me how a double would be better?
As best as I can tell, the idea is that because the home run is the very pinnacle of exhiliration in a baseball game, the letdown afterwards would sap a team of all its mojo to keep going with the rally.  Plus, it would take runners off the basepaths (by making sure that they scored!), I guess leading to despair in the fact that the next hit, unless it is also a home run, has no chance of bringing in another run.  Apparently, the only way to score several runs is to score them in a slow, steady stream rather than all at once.  They must count more if they’re gotten one at a time.
But then again, this is a testable question.  Dataset is my handy-dandy 2000-2006 PBP database from the greatest website in the world, Retrosheet.  The nice thing about a home run is that you can know for sure what the baserunner configuration will be afterwards: no one on.  The only mystery is how many outs there are.  If a homerun really does kill off a rally, then we should see that the run expectancy for these situations after a homerun will be less than if the situation hadn’t been preceded by a homerun.  I isolated all situations in which there were none on and none out and separated them into situations in which the event immediately beforehand had been a home run or whether it had been something else.  Was there a difference between the run expectancy when a HR had come right before?  Yes, there was.  The “home run” group actually had a higher run expectancy than the “other event” group (.567 vs. .534).  I ran an independent groups t-test to make sure those numbers were significantly different.  They were.
I repeated the process for situations with none on with one out and none on with two out.  Same basic results.  A homerun predicted a significantly greater run expectancy (1 out: .308 vs. .286; 2 out: .122 vs. .111).  After all, the batting team is facing a pitcher who is pitching so poorly as to give up a home run!
But perhaps I’m looking in the wrong place.  After all, I’m looking at all home runs, not just those which are hit during late rallies.  I refined my search to situations which took place in the seventh inning or later and which pulled the batting team to within 1 to 3 runs.  I looked at the run expectancy between these two groups of situations.  In all three cases (0 out, 1 out, 2 out), there was a small bump up in run expectancy after a home run, although this time it wasn’t significant.  So at the very least, a home run doesn’t take any steam out of a rally.  The difference is probably due to the fact that a very good relief pitcher is more likely to be pitching in a close/late situation.
The numbers, for the curious:
0 out: .470 for the HR group, .456 for the other group
1 out: .256 vs. .239
2 out: .094 vs. .091
Finally, perhaps there is something to the idea that an RBI double is better than a home run.  I found all situations in which there had been an RBI double that brought a team to within three runs late in the game and left only a runner at second and compared the run expectancy of that situation to the run expectancy of a runner at second in a close/late game that had happened by some other manner.
With no one out, run expectancy was 1.14 following an RBI double, while 1.07 following some other event.  The difference is not significant.  With one out, there is a significant difference, such that an RBI double makes run expectancy go down (.510 after a double, .646 after something else).  With two outs, the difference is not significant, but the trend is in the direction of an RBI double doing more harm than good (.283 vs. .297).  If something actually sucks the mojo out of a rallying team, it’s an RBI double!
Next time you hear an announcer say that a double would be better outcome than a home run for a rallying team, please be so kind as to smack some sense into them.


7 Responses to Homerun kills rally, film at 11

  1. John Beamer says:

    Nice article. The only possible reason for the rally hypothesis is that havng men on the basepaths is more disruptive than not (eg, pitching from the stretch) but that would appear to make no impact.
    I do wonder how much pitcher skill accounts for the difference in results, even when for some of the non-significant results.
    Also where has Sean gone?

    • Christopher McDaniel says:

      I know this is an old blog, but the convo never dies does it? Looking at 2013 batting data: we can examine the runs per plate appearance…with the bases empty that probability that the batting teams gets a run is .027, but with runners on it is TEN times higher at .210. Also, In 2013, with the bases empty the MLB batting average was was .250, and with at least one runner on it was .259.

      It is common sense, the odds of scoring runs increases with the bases occupied…duh.

  2. Pizza Cutter says:

    The reason I specifically tried to control the situation (close/late) was that generally the good relievers/closer will be in the game. I guess that the group of pitchers that would give up HR vs. 2B might be different, so there’s that issue to consider. You might be on to something there.
    As to Sean, I got an e-mail from the baseball director here at MVN saying that Sean just decided that StatSpeak wasn’t his thing any more. Knowing him, he’ll still be around the usual hangouts (Fever, Tango, Ballhype, etc… maybe even here once in a while). I hope whatever he does next works out for him. For an Angels fan, he’s a good writer/researcher.

  3. tangotiger says:

    A HR is typically hit by the #3 or #4 hitter, meaning that the next batter is the 4th or 5th hitter. That would likely explain the higher run expectancy (as well as the likelihood that poorer pitchers and hitter friendlier parks allow more HR than not).

  4. Pizza Cutter says:

    True that the 3 or 4 hitter would be the one most likely to hit the homerun, although wouldn’t they also be the ones most likely to hit the doubles as well?

  5. tangotiger says:

    With 23% of all PA from the #3 and #4 slots, those hitters got 23% of all the doubles+triples and 33% of all the HR.
    So, your sample is biased, in that the “next batter” is likely to be the #4 and #5 batter 33% of the time.

  6. tangotiger says:

    Comment got eaten up.
    33% of 2006 HR were from the #3/#4 slots.
    Those slots accounted for 23% of PA, and 23% of 2B+3B.

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