October 8, 2004

Aim For The Head

Rookies, RBI and Revamped Reliever Reports

by Keith Woolner

Continuing the update of some of our statistical reports, today we re-introduce our reliever evaluation reports, as well as a couple of new favorites.

As with the revisions to SNWL, I've broken down the new reliever statistics into three reports. The first looks specifically at inherited and bequeathed runners, to determine what a reliever's "fair" RA would have been, taking into account the runners on base and the number of outs both when he entered the game, and when he left.

The second report is the Relievers Run Expectation, and contains the Adjusted Runs Prevented metric familiar from the old report. Adjusted Runs Prevented measures the number of runs the reliever kept from scoring compared to an average pitcher, taking into account the inherited and bequeathed runners, as well as however many innings thrown by the pitcher himself.

The newest relief report is the Reliever Win Expectation report. This report looks not only at the run expectation the reliever faced, but also at the overall game situation, and the impact he had on the team's chances of winning the game. Relievers who pitch in high-leverage have a disproportionate effect than you'd expect from their runs prevented, and this captures that extra leverage. Win expectations are calculated compared to league average or to replacement level, and in each case with or without an adjustment for the actual quality of opposing batters faced by the reliever.

The unfamiliar acronyms in these reports are documented at the end of this article.

Another new report is the RBI opportunities report. Runs batted in, as Baseball Prospectus has been hammering on for years, are highly dependent on the number of opportunities a batter sees--that is, the number of runners on base when he bats. This new report shows the number of runners at each base, and how many of them were batted in, and the rate of RBI opportunity conversion.

Adding to the list of new reports is the Expected Win Matrix report, which is available to BP Premium subscribers. This is based on actual play-by-play data, and shows the probability of a team winning the game based on the current inning, baserunner and out state, team batting (home/away), and run differential. Only game situations that actually occurred during the season are included.

Lastly, based on several reader requests, we have two new reports showing VORP for rookie pitchers and rookie position players. However, this is looking at rookies based on the playing time requirements (130 AB or 50 IP), not service time (which is harder to come by). So in a few cases a player will be listed on the rookie report despite not technically being a rookie under MLB rules.

All of these new reports are available from 1972-2004. Enjoy.

Inherited/Bequeathed Runners report

GR - games in relief
INB - inherited baserunners
INS - inherited runners who scored
INR - inherited runs prevented
BQB - bequeathed baserunners
BQS - bequeathed runners who scored
BQR - bequeathed runs prevented (by subsequent relievers - i.e. bullpen support)
FRA - "Fair" RA -- includes inherited/bequeathed runs prevented

Reliever Run Expectation report

GR - games in relief
INR - inherited runs prevented
BQR - bequeathed runs prevented (by subsequent relief pitchers -- i.e. bullpen support)
FRA - "Fair" RA -- includes inherited/bequeathed runs prevented
APR - Adjusted Pitching Runs (a la Thorn & Palmer in "Total Baseball")
ARP - Adjusted Runs Prevented (includes inherited and bequeathed runs)
DIFF - how much a pitcher is underrated by Adjusted Pitching Runs (DIFF=ARP-APR)

Reliever Expected Wins Added report

GR - games in relief
E(W) - expected wins added, given state of game when pitcher entered
REP_E(W) - expected wins added vs. replacement level pitcher
OPP_E(W) - expected wins added, adjusted for quality of opposing batters
R&O_E(W) - expected wins added vs. replacement level, adjusted for opposition

Keith Woolner is an author of Baseball Prospectus. 
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