Baseball Toaster was unplugged on February 4, 2009.
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:
| Name | Yr1 | Tm1 | Kper9IP1 | ERA1 | Yr2 | Tm2 | Kper9IP2 | ERA2 | Diff K/9IP | Diff ERA |
| Bobby Ayala | 1993 | CIN | 5.97 | 5.60 | 1994 | SEA | 12.07 | 2.86 | 6.10 | -2.74 |
| Dave LaRoche | 1974 | CHN | 4.79 | 4.79 | 1975 | CLE | 10.28 | 2.19 | 5.48 | -2.61 |
| Rich Gossage | 1976 | CHA | 5.42 | 3.94 | 1977 | PIT | 10.22 | 1.62 | 4.79 | -2.31 |
| Bill Caudill | 1981 | CHN | 5.70 | 5.83 | 1982 | SEA | 10.44 | 2.35 | 4.74 | -3.48 |
| Luis Aquino | 1992 | KCA | 1.46 | 4.52 | 1993 | FLO | 5.45 | 3.42 | 3.99 | -1.11 |
| Rick Sutcliffe | 1984 | CLE | 5.53 | 5.15 | 1984 | CHN | 9.28 | 2.69 | 3.75 | -2.46 |
| Dickie Noles | 1984 | CHN | 2.49 | 5.15 | 1984 | TEX | 6.09 | 5.15 | 3.60 | 0.00 |
| Darold Knowles | 1974 | OAK | 3.04 | 4.22 | 1975 | CHN | 6.42 | 5.81 | 3.38 | 1.59 |
| Armando Benitez | 1998 | BAL | 11.46 | 3.82 | 1999 | NYN | 14.77 | 1.85 | 3.31 | -1.97 |
| Mike Bielecki | 1995 | CAL | 5.38 | 5.97 | 1996 | ATL | 8.48 | 2.63 | 3.11 | -3.35 |
ERAs that went down the most:
| Name | Yr1 | Tm1 | Kper9IP1 | ERA1 | Yr2 | Tm2 | Kper9IP2 | ERA2 | Diff K/9IP | Diff ERA |
| Mark Thurmond | 1986 | SDN | 4.08 | 6.50 | 1986 | DET | 2.96 | 1.92 | -1.11 | -4.58 |
| Miguel Batista | 2000 | KCA | 4.74 | 7.74 | 2001 | ARI | 5.81 | 3.36 | 1.08 | -4.38 |
| Doug Jones | 1991 | CLE | 6.82 | 5.54 | 1992 | HOU | 7.50 | 1.85 | 0.67 | -3.69 |
| Bobby Ayala | 1998 | SEA | 8.12 | 7.29 | 1999 | MON | 8.73 | 3.68 | 0.60 | -3.61 |
| Vern Ruhle | 1977 | DET | 3.66 | 5.70 | 1978 | HOU | 3.57 | 2.12 | -0.09 | -3.58 |
| Jose Rijo | 1987 | OAK | 7.32 | 5.90 | 1988 | CIN | 8.89 | 2.39 | 1.57 | -3.51 |
| Bill Caudill | 1981 | CHN | 5.70 | 5.83 | 1982 | SEA | 10.44 | 2.35 | 4.74 | -3.48 |
| Les Lancaster | 1992 | DET | 3.63 | 6.33 | 1993 | SLN | 5.28 | 2.93 | 1.65 | -3.40 |
| Mike Bielecki | 1995 | CAL | 5.38 | 5.97 | 1996 | ATL | 8.48 | 2.63 | 3.11 | -3.35 |
| Jaime Navarro | 1994 | ML4 | 6.52 | 6.62 | 1995 | CHN | 5.75 | 3.28 | -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.
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.
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