The pitching candidates are Jeremy Guthrie, Dice-K, Brian Bannister, Hideki Okajima, Joakim Soria and Rafael Perez.
I really don't know who will win this in real life. Dice-K and Okajima had problems down the stretch. My guess is it will be Pedroia or Bannister, probably the former.
For my ROY, to compare apples to apples, I'll first try to determine who was the best position player, and then who was the best pitcher. Then let them compete for the title.
Player WS WARP
Pedroia 19 5.7
Harris 13 2.6
Buck 10 3.1
Iwamura 13 3.2
Willits 15 4.2
Well that was easy. Pedroia is clearly the best position player. Now the pitchers:
Player WS WARP
Guthrie 13 5.0
Dice-K 12 6.2
Bannister 13 5.8
Okajima 10 3.7
Soria 11 4.6
Perez 8 2.6
Pretty hard for a reliever to come out ahead. They just don't amass enough innings. Soria comes close to the best of this group, though.
I'm a little put off by allowing Guthrie to win the category, since this is actually the fourth year he has pitched in the big leagues, and he's 28 years old. Even Dice-K, with all the Japanese pitching under his belt, is only 26.
I'll move forward with Pedroia, Dice-K and Bannister. Pedroia easily wins the win shares analysis. The pitchers have the edge in WARP. Here's the August/September analysis, and the key opponents analysis (Yankees/Blue Jays for Pedroia and Dice-K; Indians and Tigers for Bannister, although it wasn't really a race in his case).
Pedroia had an .831 OPS in August in September, but most of that was August. He was very ordinary in September. He had a poor OPS (.691) against the Yankees and Blue Jays.
Matsuzaka was worse down the stretch, with a 3-4 record, and a 5.93 ERA. Quite simply, he got tired. And although he was 5-2 against the Yankees and Blue Jays, it was luck that got him those wins. His ERA was 5.66.
Bannister is a different case, since he had no pennant race pressure. He nevertheless faded, with a 4.57 ERA, despite going 5-3. He did manage to go 3-1 with a 1.76 ERA against the two best clubs in his division, though.
So far I have not resorted to Win Expectancy to resolve these issues, but since I'm not able to pick among these three, that will be my tiebreaker. Win Probability Added (WPA) looks at each event the hitter or pitcher participated in and determines whether his action improved his team's chances of winning, or hurt it. You net the negatives against the positives.
Pedroia's WPA was 0.73 wins.
Dice-K's WPA was 1.68 wins.
Bannister's WPA was 0.59 wins.
I'm giving the ROY to Dice-K, even though I don't like giving the ROY to a guy who has been pitching in Japan since 1999, totally wore out at the end of the season and pitched poorly against his team's chief rivals. If I think of Japan as Triple A, it makes it a little easier.
Pedroia finishes second, Bannister third, Willits fourth and Guthrie fifth.
