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Monday, October 11, 2010
Did Cox make the right decisions in game 3?
If you are a Braves fan, you are justifiably emotional about last night’s game.
Here are the 3 major criticisms I have read:
1) Not pulling Conrad for Diory Hernandez in the 9th, for defensive purposes.
2) Kimbrel throwing a slider to Sanchez on the 1-2 count.
3) Choosing to bring in Dunn, the lefty reliever, to pitch to Huff, who has a higher BA against lefties this year.
OK, number one is a legitimate beef I think. I do no know how good a defender Hernandez is. I have a feeling that Cox never even thought of replacing Conrad in the 9th. I don’t think any of the commentators did either. No one remarked about it on TV that I remember.
Despite Conrad’s recent woes in the field, is he really that bad of a fielder? According to Chone’s TZ for the minor leagues, he was a slightly below average defender at 2B. Now maybe, with all his miscues recently, he was nervous and thus a terrible fielder at the time. I don’t know. Only someone like Cox might know that. And of course if Conrad is much the worse fielder, how much does that actually cost in terms of WE?
Number two is somewhat of a legitimate beef I think, although it is very much a 20-20 hindsight thing. If Sanchez had gotten out on that slider, no one would have said a thing. Plus, it was a little bit of a hanger. Had Kimbrel thrown that down and away, like he wanted to, again, no one likely would have said a thing. Yes, he has a good fastball, and yes, Sanchez had just swung at some fastballs out of the zone (and missed them badly), but is he supposed to throw all fastballs? He has a good slider. If he had thrown a fastball right down the middle and Sanchez had gotten a hit, fans could easily have criticized him for throwing too many fastballs. I did not think that the slider was a terrible pitch to throw in that situation. He obviously missed his location which can happen with any pitch. I don’t think there is much of a legitimate criticism here. A little maybe, as I said, but not a lot.
#3 is way off the mark, I think. There are several reasons why. First of all, despite the fact that Huff is hitting better versus lefties, BA-wise this year, all lefties batters have positive platoon splits. Virtually no lefty batter has a reverse platoon split. In fact, if you look at Huff’s last 3 years, he has a 1.15 platoon ratio for OPS, and even a 1.08 ratio for BA. If we go back 5 years, it is even higher than that. So, the idea that Huff’s higher BA against lefties in 2010 means anything (predictive) is nonsense.
Now, when you bring in a same-side pitcher, it is not just the batter’s true platoon ratio that you care about, but the pitcher’s as well. Let’s say that Huff had a 1.00 ratio or even a reverse one. If you brought in a pitcher with a large platoon ration, it still might be correct. The platoon ratio for a particular batter/pitcher matchup, like anything else, is roughly a log-5 (odds ratio) combination of the pitcher and batter’s ratio.
And obviously the overall true talent of the pitcher has to be considered as well. If you bring in an overall (much) worse pitcher just to get a platoon advantage, it still might not be correct, although when you bring in lefty against lefty, in most cases you gain so much from the platoon advantage that even a mediocre overall lefty becomes a very good pitcher when facing a lefty batter.
So what about Dunn? What is his true platoon ratio? In a small sample, his MLB career platoon (OPS against) splits are large - 1.29.
For all pitchers, I compute estimated platoon splits from their actual numbers in the majors and minors, regressed the appropriate amount, given the types of pitches (and frequencies) they throw. For Dunn, I have that number at 1.27. For Kimbrel, based on his minor league stats, I have that at 1.31 (mostly because he throws the 2 pitches with the highest platoon ratios - fastball and slider). So it looks like Dunn is WAY the better choice for Huff than Kimbrel. What about Moylan or Farnsworth? Moylan is a siderarmer. He has an estimated true split of 1.41. And Farnsworth’s is 1.21, also a large platoon split, probably because he throws mostly fastballs I think.
Finally, I also, in my computations, estimate the average ERA that a reliever would have against RHB and LHB with average platoon splits:
Dunn
vs. RHB: 3.80
vs. LHB: 3.03
Kimbrel
vs. RHB: 2.91
vs. LHB: 3.75
Farnsworth
vs. RHB: 3.23
vs. LHB: 3.93
Moylan
vs. RHB: 3.51
vs. LHB: 4.86
So, it looks like Dunn was clearly the right choice, even if Huff had a slightly smaller platoon split than the average LHB (and there is not much evidence that that is the case - in fact, my estimated OPS true platoon split for him is quite high - 1.21 ).