Relief Expectations

One of the quotes from David Laurila’s column yesterday also resonated with me:

“When (Tim Worrell) was setting up with the Phillies, Billy Wagner was the closer… the bullpen phone would ring in the eighth inning and it was, ‘Worrell is in the game.’ Wags used to look at him and just laugh, because it was the middle of the lineup.” — John Gibbons, Blue Jays manager, July 2017

It struck me that one way of measuring this would be to figure out the expected value of various statistics based on the actual batters faced. I tried this out with On-Base Percentage* (OBP*), and the results are in this spreadsheet.

*For this study, I’m using (Hits+Walks+HBP)/BFP (or PA for batters) for the OBP. That’s different than the definition for the MLB stat, but works better for this study.

I base everything on a season. For batters, I regress their OBP* to the MLB average if they have less than 200 PA during the season. Using that, I can figure out the expected OBP* facing the pitcher, and compare it to the actual OBP* the pitcher allowed with the following index:

100*(OBP*)/(Expected OBP*)

The lower the number the better the pitcher performed against expectations.

I used the spreadsheet to calculate three more columns. First, the high and low values of the 95% confidence interval based on the number of BFP and the Expected OBP*. Finally, a binary column indicating if the pitcher’s actual OBP fell outside that range (1 if it did). This provides a way to see quickly if more than luck was involved in a good or bad index.

The spreadsheet covers seasons from 2011-2017 (current decade). At first glance, Koji Uehara‘s 2011-2013 stand out as consistently great seasons.

As for Wagner and Worrell, they pitched together during all of the 2004 season. Worrell had an Expected OBP* of .338, and an actual OPB* of .300 for an 88.7 index. He was good. Wagner had a n Expected OBP* of .333 with an actual OBP* of .214 for an index of 64.4. Worrell was getting the tougher assignments, at least in terms of batters getting on base.

from baseballmusings.com http://ift.tt/2EqmMdL