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Circuit Breakers
2005-04-07 22:29
by Mike Carminati

My friend Mike shot me an email on opening day that Pedro Martinez had nine strikeouts through four innings. Being a diehard Yankees fan and a putative Mets fan, he was conflicted as to the rooting protocol for the ex-Red Sock. Being a Phils fan myself who grew to hate the Zimmer-tossing, Posada-baiting, dwarf-loving, daddy-seeking pitcher even before he pitched for the Mets, I was conflict-free.

However, being a baseball fan first and foremost, I would root for the devil himself (or a Ray Walston-ian equivalent) if he were pitching a perfect game. So when Pedro ended up with twelve Ks in six innings, I felt a slight twinge of sorrow (among the uproarious laughter) that he got a no-decision for his efforts as the Mets lost 7-6 after Braden Looper gave up three runs in the ninth.

It did get me to think about the affect that pitching in a new league has on a pitcher. Look at Clemens resurrection upon becoming an Astro last year.

So what does a league change do to an average pitcher? Does he become a world beater? Are the batters, many of whom may never have faced the pitcher before, completely overpowered? Do strikeouts-per-nine-innings ratios go through the roof?

I ran a study looking at all pitchers who threw at least fifty innings in one league and then switched to the other either midseason or at the end of the season and then pitched at least fifty in the new league. I also looked at only the past 35 seasons, during which strikeout ratios went through the roof. I found 566 pitchers.

Guess what I found. K per 9 IP ratios went down an average of eight points. If you sum all stats for all pitchers found they went down by six points.

ERAs did drop by 10 points on average or 9 points based on total stats.

The pitchers whose Ks per 9 IP went up the most:

NameYr1Tm1Kper9IP1ERA1Yr2Tm2Kper9IP2ERA2Diff K/9IPDiff ERA
Bobby Ayala1993CIN5.975.601994SEA12.072.866.10-2.74
Dave LaRoche1974CHN4.794.791975CLE10.282.195.48-2.61
Rich Gossage1976CHA5.423.941977PIT10.221.624.79-2.31
Bill Caudill1981CHN5.705.831982SEA10.442.354.74-3.48
Luis Aquino1992KCA1.464.521993FLO5.453.423.99-1.11
Rick Sutcliffe1984CLE5.535.151984CHN9.282.693.75-2.46
Dickie Noles1984CHN2.495.151984TEX6.095.153.600.00
Darold Knowles1974OAK3.044.221975CHN6.425.813.381.59
Armando Benitez1998BAL11.463.821999NYN14.771.853.31-1.97
Mike Bielecki1995CAL5.385.971996ATL8.482.633.11-3.35

ERAs that went down the most:

NameYr1Tm1Kper9IP1ERA1Yr2Tm2Kper9IP2ERA2Diff K/9IPDiff ERA
Mark Thurmond1986SDN4.086.501986DET2.961.92-1.11-4.58
Miguel Batista2000KCA4.747.742001ARI5.813.361.08-4.38
Doug Jones1991CLE6.825.541992HOU7.501.850.67-3.69
Bobby Ayala1998SEA8.127.291999MON8.733.680.60-3.61
Vern Ruhle1977DET3.665.701978HOU3.572.12-0.09-3.58
Jose Rijo1987OAK7.325.901988CIN8.892.391.57-3.51
Bill Caudill1981CHN5.705.831982SEA10.442.354.74-3.48
Les Lancaster1992DET3.636.331993SLN5.282.931.65-3.40
Mike Bielecki1995CAL5.385.971996ATL8.482.633.11-3.35
Jaime Navarro1994ML46.526.621995CHN5.753.28-0.77-3.35

You say there are too many relievers whose stats are at the mercy of certain vicissitudes of the teams they happen to face. Let's set the minimum to at least 100 innings.

No good. Ks per 9 IP drop by 10 points on average (11 for totals). And ERAs drop by just 8 on average (3 for totals).

OK, so what does this tell us? I think a change of league just adds another variable to a pitcher's season. Perhaps some thrive after the change of scene, and those are the ones we remember, building up our anecdotal evidence. But on average change league don't mean diddley.

2005-04-08 08:51:36
1.   Mike from Hoboken
My perception has been that pitchers have an easier time going to the National League than the American. Since I'm too lazy to look closely at the numbers myself, is there anything in your data that would support or debunk this?
2005-04-08 09:45:41
2.   afmaury
I don't have the data to prove it, but I would say that it is generally easier going to the NL than AL. Overall, I believe the NL scores less and hits worse than the AL due to a pitcher in the lineup rather than a DH. Therefore, a pitcher's numbers should improve with a swith to the NL.
2005-04-08 11:37:11
3.   Mike Carminati
I'll run the data later today comparing AL-to-NL and NL-to-AL totals.
2005-04-08 18:19:26
4.   Mike Carminati
Pitchers with a min. of 50 IP per season/stint, who went from the NL to the AL saw their K per 9 IP drop by 32 points and their ERAs rise by 21.

AL to NL? K per 9 IP rose by 18 pts and ERA fall by 43.

How much of that is attributable to having to face pitchers who bat in the NL and ballpark affects is not readily apparent. That's a study for another day.

2005-04-09 07:27:37
5.   Devin McCullen
Isn't it generally true that pitcher's K rates decline as they get older? Are the results that much different than a similar group of players who didn't switch leagues?
2005-04-09 09:08:51
6.   Mike Carminati
Pitchers who threw at least 50 innings in a year/stint in one league and then pitched another 50 in the next year/stint in the same league saw their K per 9IP drop 6 points and ERAs rise 13.

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