Craig Burley was right... Yankees have best rotation in A.L. (or do they?)
Thursday, July 24 2003 @ 10:02 AM EDT
Contributed by: robertdudek
The basis of Craig's hypothesis is the fact that the Yankees are comfortably ahead of the pack in terms of DIPS ERA (DIPS is an acronym coined by Voros McCracken for Defence Independent Pitching Stats). DIPS ERA assumes that pitchers control only HBP, W, K and HR and then fills in the rest of the stats based on league average performance, so that the effects of "fielding" are filtered out.
There's one little problem. Even fielding-independent stats need to be park adjusted. How do we adjust these for home and road park of a given team/pitcher? Taking a general park factor (i.e. the impact of the park on runs scored in general) isn't going to work because we only want to adjust the fielding-independent events, as the fielding-dependent events are adjusted by DIPS to league average.
What we need is a set of event park factors, that is, an estimate of how a park affects the frequency of each event (2B/3B, HR, W, K, singles etc). I calculated a series of composite park factors (they take home and road parks into account) for the 2003 American League to date for a number of different events. One important assumption I will make is that batters faced remains constant. Here are the results.
Team ....... W rate K rate HR XBH Singles
Chi Sox ...... 1.0072 1.0053 1.1994 0.9958 0.9720
Toronto ...... 0.9862 1.0207 1.0492 1.0980 1.0112
Texas ...... 0.9406 0.9919 1.0342 1.0730 1.0321
Baltimore ..... 1.0581 0.9953 1.0332 0.9213 0.9686
Seattle ....... 1.0157 0.9868 1.0105 0.8546 1.0039
Anaheim ....... 1.0068 1.0042 1.0029 1.0752 0.9843
Minnesota ..... 0.9644 1.0436 0.9932 1.0017 1.0271
Kansas City ... 1.0619 0.9038 0.9810 0.9908 1.0011
New York ...... 0.9880 1.0003 0.9566 0.9537 0.9827
Tampa Bay ..... 1.0670 1.0156 0.9532 1.0292 1.0255
Oakland ....... 0.9492 0.9456 0.9514 0.9988 0.9715
Cleveland ..... 1.0744 1.0329 0.9174 0.9880 0.9827
Boston ........ 1.0013 0.9387 0.9170 1.0301 1.0284
Detroit ....... 0.9472 1.0160 0.8983 0.9049 1.0003
Notes: a figure greater than 1 indicates that the environment increases the frequency of the event; HBPs remain unadjusted; XBH is doubles and triples combined.
What we now must do is adjust each of the revelant events using the appropriate park factor, being careful to take secondary effects into account (e.g. a park that decreases the frequency of homeruns will increase the frequency of balls in the field of play). It may also be useful to compare a DIPS RA with both the original Run Average and a park-adjusted Run Average using the general park factor.
American League Starting Pitchers by Team, sorted by DIPS RA
Team .......IP/start RA adjRA DIPS-IP/start DIPS RA
New York ..... 6.61 4.42 4.73 6.75 4.14
Boston ....... 5.87 4.77 4.44 5.95 4.34
Chi Sox ...... 6.29 4.40 4.28 6.21 4.54
Oakland ...... 6.47 4.05 4.41 6.36 4.64
Baltimore .... 5.94 5.08 5.53 6.09 4.77
Toronto ...... 5.91 5.47 5.00 6.04 4.80
Seattle ...... 6.43 4.03 4.33 6.24 5.01
Minnesota .... 5.97 5.35 5.19 6.00 5.14
Kansas City .. 5.74 4.80 4.25 5.72 5.16
Cleveland .... 5.76 5.22 5.52 5.68 5.41
Detroit ...... 5.69 5.41 5.69 5.63 5.56
Anaheim ...... 5.77 5.14 5.32 5.77 5.58
Texas ........ 4.97 7.04 6.58 5.05 5.97
Tampa Bay .... 5.32 6.25 6.18 5.30 6.06
Key: IP/start = number of innings per start by the starting pitchers; RA = actual runs divided by actual innings multiplied by 9; adj RA = park-adjusted runs per 9 innings, using a general park factor; DIPS IP/start = innings per start adjusted for park and assuming a league average defence; DIPS RA = runs per 9 innings adjusted for park and assuming league average for all fielder-dependent events.
The Yankees have put up the best DIPS RA and work deeper into the game than anyone else. However, they only rank 6th in adjusted Run Average. I'll let the readers draw their own conclusions about this.
You may ask why the defence-independent IP/start are different than actual IP/start. There are two reasons: 1) park-adjusting walks, strikeouts and homeruns will cause the number of baserunners to change - thus increasing or decreasing the number of outs if batters faced remains constant; 2) substituting a league average defense may convert more or fewer balls in play into outs.
Park-adjusted Run Average is a good rating of the overall pitching/defensive performance of a team, but is defence-independent Run Average a similarly adequate assessment of the quality of pitching in isolation? DIPS RA purports to filter out the effects of defence, but it also filters out other skills the pitcher possesses which may impact run scoring. For example, a pitcher may be a good or bad fielder (think Greg Maddux and Kelvim Escobar on a ball hit up the middle), he may be good or bad at shutting off the running game or inducing easy double play balls, or he may be good or bad at working out of a jam. Finally, a pitcher may be good or bad at inducing easy outs on balls hit in play (chiefly pop ups and weak grounders). All of these things are filtered out in DIPS RA as well.
This leads me to believe that the truth lies somewhere in between DIPS RA and park-adjusted RA, perhaps a bit closer to the former.
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