The Baseball Graphs Blog

Monday, May 29, 2006

WPA in the ninth

This article from the Sox Watch site has a great insight into scoring WPA for some important, complicated plays.

The final play was a tricky one, and an important one for WPA, because there was a lot on the line at that point, obviously. The Sox WP before the play was 85.4%. Crawford got a base hit to right, scoring Norton, and then Harris threw out Gathright trying to score. On plays like this, I split the action into two separate plays. First, Crawford’s hit scores Norton. If the play had stopped there, we would have had a 5-4 score, with the bases loaded, with a Sox WP of 76.2%. Tavarez therefore takes a -0.092 WPA debit for his role in the play.

From here on, however, Tavarez is not involved in the play, and so all the remaining WPA credit/debit is split among the fielders involved. We start with a WP of 76.2% and the ball in center field, and we finish with Gathright out at the plate, the game over, and a WP of 100%. There is therefore 0.238 of WPA to be distributed. I elected this to split this into three equal parts: One share went to the “Errors” category, which represents errors (and also good plays) by the opposing team. In this case, I consider Gathright’s decision to try for home to be a judgement error.

It’s not clear at this point whether Gathright was waved home or made the call on his own, but in any case, it was a poor decision that helped the Sox. The remaining two-thirds of the credit for this play I split evenly between Harris, who threw a perfectly-located strike to the plate, and Mirabelli, who hauled it in, got set, and made the tag on Gathright.

There is no “correct way” to calculate the WPA of plays like this.  But in general, splitting a play into components and logging each one separately is the best way to handle it.


Posted by Studes on 05/29 at 06:25 PM
Win Probability AddedPermalink
Tuesday, May 23, 2006

Historic FIP

Cyril Morong has created a historical look at the greatest FIP years for individual pitchers.  FIP, which stands for Fielding-Independent Pitching, is a relatively simple yet powerful pitching stat.  It weights strikeouts, walks and home runs—those things that a pitcher is solely responsible for—to produce a fair ERA without all the surrouding “noise” of bloop hits and bad fielders.

Cyril did some more things to standardize FIP even further.  His weights are slightly different than ones I’ve used in the past, he didn’t create specific ERA constants for each year and he “normalized” the range of strikeouts, walks and home runs in each year.  I guess these are “ultra-normalized” FIP’s but I wonder if sometimes stats become so sanitized that they lose value instead of adding insight.

It would be good to see some more discussion of why he added his extra calculations and what the impact of them was.


Posted by Studes on 05/23 at 02:16 PM
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Monday, May 22, 2006

The Blue Jay WPA Way

Thomas has a nice post up on Batter’s Box analyzing the Blue Jay’s bullpen with WPA.


Posted by Studes on 05/22 at 10:38 AM
Win Probability AddedPermalink
Friday, May 19, 2006

Fielding Win Shares

J.P. has a nice review of fielding Win Shares in his blog, inspired by the 2006 Win Shares posted at the Hardball Times.  Here are the links to his main posts:

Outfield Defensive Win Shares
Tweaking Defensive Win Shares
More Defensive Talk

I agree with J.P. that fielding Win Shares should have negative totals for certain players (something Bill James would almost certainly disagree with) but he underestimates how hard it would be in this post.  Essentially, giving players negative fielding Win Shares would require totally different formulas than the current ones.


Posted by Studes on 05/19 at 02:18 PM
Win SharesPermalink
Thursday, May 04, 2006

The Latest Spreadsheet

I’ve uploaded a new version of the WPA spreadsheet.  I’ve added a “poor man’s” Leverage Index to the spreadsheet, replacing Doug Drinen’s “P” as a way to measure the criticality of a situation.  This Leverage Index is based on the difference between the Win Probability of the current situation and the Win Probability of a strikeout (in that situation).  This approach was suggested by Tangotiger, and it seems to follow the distribution of his Leverage Index pretty closely.

If you’re using the WPA spreadsheet (particularly if you’d like to track the crticiality of each situation), I suggest you start using this version (1.7).  As always, please let me know if you find any problems with it.

The spreadsheet (which requires Windows Excel 2002 or later) can be downloaded from ftp://ftp.baseballgraphs.com/wpa

Don’t rename the spreadsheet, or you’ll lose the macros!


Posted by Studes on 05/04 at 07:19 PM
Win Probability AddedPermalink
Wednesday, May 03, 2006

Timeline graphic

I have a fascination with timelines, especially ones that can help us grasp the length of time it takes certain things to happen.  Along those lines, you can’t beat this java timeline that covers everything from the Big Bang to the present day.  Highly recommended.


Posted by Studes on 05/03 at 03:22 PM
GeneralPermalink
Monday, May 01, 2006

WPA developments

There are two “historic” landmarks today in the world of Win Probability Added.


Posted by Studes on 05/01 at 05:02 AM
Win Probability AddedPermalink