SIERA's for Yankee Prospects

Written by Sean P | 01 March 2010

Baseball Prospectus, while unveiling a new team of writers also has unveiled a new statistic called SIERA that Greg touched on before here.

As a quick refresher, here is what SIERA does:

1. Allows for the fact that a high ground-ball rate is more useful to pitchers who walk more batters, due to the potential that double plays wipe away runners.

2. Allows for the fact that a low fly-ball rate (and therefore, a low HR rate) is less useful to pitchers who strike out a lot of batters (e.g. Johan Santana's FIP tends to be higher than his ERA because the former treats all HR the same, even though Santana’s skill set portends this bombs allowed will usually be solo shots).

3. Allows for the fact that adding strikeouts is more useful when you don't strike out many guys to begin with, since more runners get stranded.

4. Allows for the fact that adding ground balls is more useful when you already allow a lot of ground balls because there are frequently runners on first.

5. Corrects for the fact that QERA used GB/BIP instead of GB/PA (e.g. Joel Pineiro is all contact, so increasing his ground-ball rate means more ground balls than if Oliver Perez had done it, given he's not a high contact guy).

6. Corrects for the fact that FIP and xFIP use IP as a denominator which means that luck on balls in play changes one's FIP.

Needless to say this information is extremely useful in determining skills that pitchers can control and predicting future ERA. What we didn’t know a few weeks ago was that Baseball Prospectus also has SIERA numbers for minor leaguers, included in their annual season preview book. Let’s take a look at the SIERAs they provided.

Manny Banuelos,  2.67 ERA, 3.22 SIERA

Jeremy Bleich,  6.65 ERA,  4.18 SIERA

Wilken De La Rosa,  3.48 ERA,  4.11 SIERA

Zach McAllister,  2.23 ERA,  3.82 SIERA

Hector Noesi,  3.92 ERA,  2.64 SIERA

Ivan Nova,  AA- 2.36 ERA,  4.30 SIERA/ AAA- 5.10 ERA,  4.68 SIERA

Romulo Sanchez,  4.04 ERA, 4.00 SIERA

Andrew Brackman,  5.91 ERA,  4.40 SIERA

DJ Mitchell,  2.87 ERA,  3.54 SIERA

David Phelps,  2.80 ERA, 3.67 SIERA

SIERA’s are pretty complicated and involve a lot of factors so I don’t think I could illuminate every single thing causing the discrepancies that appear here. However some of it has to do with adjusting for park, league, defense, ground ball percentages as well as BABIP, K% and BB%.

A couple of things really stand out however. Hector Noesi is one of the few pitchers who has his SIERA almost a full run lower than his ERA. This isn’t a fluke either, as Noesi has consistently had sub 3.00 SIERA’s at each level for the past 2 seasons. Noesi is a fly ball pitcher and control specialist but has also struck out almost a batter per inning at each level from 08-09 as well. Andrew Brackman who had a horrific season shows a more reasonable SIERA of 4.40 compared to his 5.91 ERA in Charleston. Some of this is adjusting for defense I would assume as well as his elevated BABIP of .325 and a reasonable K%. However there’s really no glossing over such a bad season. If your still burning a torch for Brackman, BP does it’s best to douse it with water:

“The most wrong-headed first round pitching selection since Bill Bene, Tomy John surgery survivor Andrew Brackman was healthy enough to completely destroy any remaining illusions about his being a prospect at all- mechanical consistency is no more than a concept”

Ouch. Zach McAllister had a really low BABIP of .266 and playing in Trenton it’s not surprising the 2.23 ERA might be misleading. BP actually has McAllister with only a 47% GB rate in Trenton as well which is surprising from sinkerball specialist. McAllister has consistently had SIERA’s in the mid 3’s, which is obviously very good but not as nice as the 2.23, 1.84 and 2.45 ERA’s he’s posted the past two years.

In the next few weeks we’ll post some of the projections and discuss what the various systems have to say about the Yankee prospects they have numbers for. We’ll also be wrapping up our last 5 Yankee prospect profiles as well as starting to cover their spring training performances. It’s almost a month until real baseball and we’re getting pretty excited.