Anyway, Cubs Stats readers may recall my previous post, which both explained SIERA and applied it to the 2009 Cubs. In that post, we discovered SIERA dislikes these pitchers:
The Kind-of Losers (anyone with a higher SIERA than xFIP)
Sean Marshall: (SIERA) 4.01, (xFIP) 3.82
Randy Wells: 4.34, 4.24
Carlos Silva: 5.65, 5.38
Now, what I found most intriguing about the differences in SIERA and xFIP is that the maximum gain from SIERA was around 0.94 (Russ Springer) and the maximum loss was equally close to 1 (J.J. Putz). In other words, there is really not a whole lot of variation there. But, considering SIERA uses a lot of similar inputs as xFIP, we should expect that any variation is pretty close to being significant (even if it is not statistically significant, which is a whole different can of worms).
So what are the profiles of these pitchers that SIERA would punish them? Or, more importantly, do any of these pitchers have profiles more akin to recieving SIERA's blessing rather than spurning?
Sean Marshall earned some above-average ground ball rates (GB%), but his strikeouts and walks were close to league average (K/BB 2.13; league average is about 2.00, and higher is better). Also, he had a normal home run rate. Therefore, SIERA doesn't see anything to reward.Ultimately, it again appears that SIERA has done a pretty good job identifying what the marginal statistics confirm. With the exception of Carlos Marmol, I can't think of any SIERA results that left me scratching my head.
Randy Wells had a great rookie season, but was also pretty lucky. Almost every metric tells us that. He had an unusually low HR-rate (0.76 per 9 IP; league average is about 1.00) with fewer strikeout than you would like for a guy giving up a standard amount of flyballs. In other words, SIERA can see through the luck, too.
Carlos Silva really only pitched a handful of games in 2009, a total of 30 IPs. It's hard to critique on that small of a sample, but SIERA rightly detects that: a) he struck no one out and b) surrendered long balls like mad.