david@fisher.UUCP (David Rubin) (08/01/85)
At the end of this article is a list of the top pitchers in both leagues in terms of Earned Runs PREVENTED. What is ERP? Allow me to first answer: why ERP? Traditional statistics for comparing pitchers' performances are flawed. Win-Loss records favors good pitchers on good teams over great pitchers on lousy teams. ERA, while a substantial improvement, does not allow for the fact that a pitcher with a 1.80 ERA over 50 innings is not as valuable as a pitcher with a 2.10 ERA over 250 innings. ERP solves both these problems. As a good record is kept of which runs can be attributed to pitching (earned) and which to fielding (unearned), we can count the number of runs a pitcher allows, the number of innings pitched, and ask how much better or worse than an "average" pitcher in the same league did the pticher in question do. Thus ERP: the number of earned runs a pitcher allows subtracted from the number of earned runs an "average" pitcher would have yielded over the same number of innings. It can be calculated from readily available statistics as follows: ERP = (League ERA - Pitcher's ERA)*IP/9 Some might argue that "earned" and "unearned" are too poorly determined to have any use in determining a pitcher's performance; however, if this were the case, we would expect little consistency in ERA performance from year to year, which is not the case. My critique of ERP is that pitchers have different roles, and the run prevented by a ninth-innning stopper is likely to have more value than the run prevented by a starter or especially by a long reliever put on the mound in a blow out. Thus, I'd advise caution when comparing between pitchers playing different roles, but am a strong advocate of ERP as a standard of comparison among pitchers who have the same role. Here, then, are the leaders as of 0000 July 31: National League American League (Avg ERA = 3.43) (Avg ERA = 4.07) Pitcher, W-L ERA IP ERP Pitcher, W-L ERA IP ERP Gooden, 16-3 1.65 180 35.5 Stieb, 10-6 1.96 170 39.7 Vlnzuela, 12-8 2.14 176 25.2 Key, 9-4 2.69 141 21.6 Andujar, 17-4 2.31 176 22.0 Guidry, 13-3 2.88 162 21.4 Tudor, 12-8 2.23 161 21.5 Saberhgn, 12-5 2.85 149 20.2 Hesketh, 8-4 2.25 132 17.3 Morris, 12-6 3.04 175 20.0 Dravecky, 8-6 2.26 132 17.2 Seaver, 11-8 3.08 164 18.0 Hrshiser, 11-3 2.41 142 16.1 Hrnandez, 5-4 1.92 75 17.9 Garrelts, 5-3 1.47 73 16.0 Moore, 7-4 1.48 61 17.6 Cox, 12-6 2.54 160 15.9 Romanick, 12-4 2.94 138 17.3 Burke, 5-0 1.51 66 14.0 Witt, 8-7 3.16 165 16.6 Now you know who SHOULD expect to get Cy Youngs; Gooden and Stieb have led their leagues for some time now, and continue to pad their leads. No one is likely to catch them. Unfortunately, W-L records are given undue weight. Thus there appears to be a danger that the clearly superior pitcher in the AL will be passed over; the danger in the NL is not as acute, as Gooden has the glamorous record and the strikeouts to aid his campaign. Write to your local sportswriter on behalf of Dave Stieb now! David Rubin {allegra|astrovax|princeton}!fisher!david P.S. It also says a lot about Dick Williams methods of choosing a starting pitcher for an All-Star game, but far be it from me to pick at that sore again... P.P.S. ERP was first proposed by John Thorn and Pete Palmer in "The Hidden Game of Baseball"; to this statistic they have converted me, with the one reservation expressed above. The New York Times publishes slightly unusual statistics for the top 10 ERP pitchers in each league every Thursday, from which the above list was distilled.