Looking at how to analyze alleged “second-half” players”.

In a recent podcast, a fantasy baseball “expert” was discussing the expected rebound of certain alleged “second half” players. The podcaster listed certain pitchers that he thought would have second half rebounds. Why am I mentioning this as a fallacy?? Well, maybe it is true in some instances, but here, specifically are the players mentioned by this podcaster:

Matt Cain, Erik Bedard, Kelvim Escobar, Jon Garland, Joe Nathan, Francisco Cordero, Francisco Rodriguez.

These are all very talented pitchers; with the possible exception of Garland all have tremendous skills that needn’t be addressed here; we all know them. The premise of the podcast was that these were all “second half” players, because they all performed appreciably better in the second half last year. Do you see the problem here?

Just to look at one or two here (since the point is easily made) here is a look at Joe Nathan. As I am writing this he has a 2.59 ERA, 1.40 WHIP, 14 Saves. Presumably the podcaster was looking at that WHIP and relatively meager save total. So, he said that he felt Joe Nathan would rebound in the second half, since he has a history of “second half rebounds.” However, the podcaster only mentioned the 2006 season. So let’s even assume that there was a “history.” Will this be the driving force behind any second half improvement?

Nathan has a 38% hit rate, which is astoundingly high for a pitcher of his caliber. Even for a pedestrian pitcher we would expect a regression to the mean of 30% on a going forward basis. Nathan has, in his career, never allowed a BABIP of more than .300, yet now he is close to .390. If he improves will it be because he is a “second half player?”

Looking at Erik Bedard, we see (as of this writing) a 3.60 ERA, 1.23 WHIP 10.9 K/9IP and 2.8 BB/9IP. This is a stud pitcher. He has a 33% hit rate, which is 3% above the norm, though Bedard has always been above the 30% benchmark, surprisingly. Given the K rate and BB rate (with a ratio of 3.9, which is excellent) and a somewhat unlucky hit rate, perhaps his ERA should be a bit lower. If he has a tremendous second half would anyone be surprised?? He is a stud right now, and a stud should have a great second half. This isn’t because he had a good second half last year; he is just a good pitcher.

Matt Cain is an even more puzzling example. 2006 was his first full year in the majors. Is it any wonder that he had a good second half? He was learning the league, and was about one year into his career (since he had roughly a half year in 2005). Moreover, he was very unlucky with bullpen help in the first half, when only 64% of his runners were stranded (second half was a normal 73%). His improved second half, again, was not because of any innate ability to perform better in the second half, it was normalization of his statistics. Why this podcaster would make a prediction on a second half sample size of one is puzzling.

When I am looking for second half rebounders, or any “buy low” candidates, I generally don’t go about it by looking at their historical splits. They may be valid they may not be. But to make the prediction on those grounds is lazy. Looking at their overall skill package, and whether they have been lucky or unlucky in relation to their skills is how you find them. I hope that the Fantasy General will not fall into this trap.