bullpen by gmLI

by jacob on May 5, 2008 10:07 AM CDT

Dwarf Grit Report as of 5/05/2008. Yost preserves bullpen pecking order.

gmLI            4/28  5/05 
Eric Gagne      2.16  2.15
Guillermo Mota  2.13  1.86
Brian Shouse    1.82  1.57
Salomon Torres  1.51  1.42
David Riske     1.34  1.21
Mitch Stetter   1.32  1.13  
Seth McClung    1.12  0.94
Derrick Turnbow 1.03  0.90

gmLI: A pitcher’s average LI when he enters the game.
LI (leverage index): A measure of how important a particular situation is in a baseball game depending on the inning, score, outs, and number of players on base, created by Tom Tango.

data and definitions from fangraphs

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Is there a way to calculate their gmLI for the next pitcher?

As a proxy for how effective the reliever did their job, they should make the situtation at least no worse than they entered it normalized for the increase in LI as the game moves closer to completion. Has anyone heard of such a thing, or would this be too cumbersome to calculate?

by Getting Yosted on May 5, 2008 11:42 AM CDT reply actions

you're basically describing WPA

which is on display in all of the fangraphs boxscores, and I think it’s on the fangraphs player pages as well.

Also, cheese.

by Jeff Sackmann on May 5, 2008 12:08 PM CDT up reply actions

yes.

on a player page, fangraphs has 5 different leverage index stats.

pLI: A player’s average LI for all game events.
phLI: A batter’s average LI in only pinch hit events.
gmLI: A pitcher’s average LI when he enters the game.
inLI: A pitcher’s average LI at the start of each inning.
exLI: A pitcher’s average LI when exiting the game.

See turnbow’s page, and you’ll notice when he comes in, his average LI is 0.90, and when he leaves (exLI) it’s 0.62, in his case this is a bad thing, an out of reach game got further out of reach. Look at Marmol’s page though, he’s the kind of guy who comes in high leverage situations, and then leaves the game in lower level situations cause he’s getting the team of jams.

So you can look at the various leverage states to see how games changed while a reliever is pitching, but you can’t really draw any conclusions from it. What you want is, just like Jeff says, WPA. That shows, with the leverage index accounted for, how effective a reliever was in directly contributing to the win. The higher the leverage index the more win probability added (or lost).

here’s the 2008 relivers by WPA, resort it and you find guys like gagne and turnbow on the negative side.

Bring Back The Old Logo!

by jacob on May 5, 2008 12:55 PM CDT up reply actions

also

i forgot to point out, that if you resort it and look at the guys with the most negative WPA, you are typically looking at guys who were misused. So go to 2007, sort ascending WPA for relievers and notice Greg Aquino is #10 on the list, in just 14 innings, he accumulated enough win probability lost to be in the top 10 least effective relievers. that’s astonishing. that’s a lot more than just bad pitching, that is horrible misuse. Look at turnbow, he’s had, what, one good outing this year, has pitched way, way worse than aquino did in ‘07 and has a WPA of “just” -0.41. That is because he has been properly used this year. junk time. his horrible outings have done much less damage than they could’ve.

Bring Back The Old Logo!

by jacob on May 5, 2008 1:03 PM CDT up reply actions

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