Interesting that the first thread I opened up on this site contains a couple of quotes I made over on S.o.S.H. yesterday (the first four lines came from me).
If anyone is interested, here is a detailed analysis I did on Arroyo about back in February:
Year Age Team W-L TBF BB/BF 1B/BF 2B/BF 3B/BF HR/BF ToP ExR R/BF Diff SO/BF GO/BF FO/BF G/F RE/BF HB/BF
2004 27 BOS 10-9 764 .062 .135 .062 .005 .022 .359 .116 .130 +.014 .186 .297 .285 1.04 .016 .026
2005 28 BOS 14-10 878 .062 .145 .064 .009 .025 .390 .126 .117 -.009 .114 .303 .358 0.85 .008 .016
Its a little difficult to tell much from Arroyo's numbers, since we are working largely on a set of two seasons. His numbers as a starter in Pittsburgh in 2000 and 2001 are probably not germane, since he is a quite different pitcher now.
Arroyo is an extreme fly ball pitcher with a career 0.98 GO/AO ratio. He tends to keep the ball in the park fairly well, but he was absolutely destroyed by doubles off the Monstah. His home/road and RHP/LHP are quite normal for a right-handed pitcher, except for his doubles rates. Here are his 2004 splits for doubles:
Although I don't have the exact splits for 2005, a glance at his HR rates and SLG rates indicate that 2005 was probably similar in splits.
This is the primary reason why Arroyo is a much better pitcher on the road. The fact that right-handed hitters, whom he handles pretty well in all other respects, hit doubles at a higher rate than lefties is completely a factor of Fenway Park.
If you took his 2004 season and put him in a PF-neutral park, his expected runs would have been .008 lower, making him a solid number 2/3 starter in the league. If any player might be expected to improve with a change of venue, its Arroyo.
Arroyo's K-rate is bothersome. His high (.186) rate in 2004 was probably higher than should be expected, but his huge dropoff (to .114) is probably also an abberation. I would expect him to increase, but probably no higher than .150. One interesting sidebar to his drop in K-rate was that he actually increased his P/BF from 3.68 to 3.76, which means that either the league was a little more patient with him (sitting on certain pitches?) or that he was just throwing more balls out of the strike zone. Normally higher pitch rates are associated with higher walk (same as 2004) and/or K-rates.
Its interesting that of his total outs, the dropoff in strikeouts was almost all converted into fly balls. His GO rate only increased by .006, while his FO rate increased by .073. In actuality then, his drop in strikeouts probably had minimal impact on his runs allowed, since they were almost all converted into non-productive fly outs. Although his 2004 season was theoretically more successful in all respects to his 2005 season, he actually allowed .013 fewer runs per batter in 2005. Although his ground out rate stayed nearly the same, infield defensive support was significantly better in 2005 than in 2004. For an extreme fly ball pitcher with a medium high K-rate, his underachievement of .014 runs more than expected can be traced to two factors: his significantly high HBP rate (which isn't factored normally into ToP and ExR) and poor defensive support (.016 batters reaching on an error). In 2005 he cut his HBP numbers significantly and his defensive support was quite a lot better.
Overall, Arroyo is something of an enigma. He has nasty stuff, but he makes a lot of mistakes. Those mistakes are almost exclusively deep fly balls - doubles in Fenway. His drop in K-rate is probably less significant than it might seem, given that fly balls are really his bread and butter. If there were a way for the Sox to use him more on the road than at home, he would probably be more effective. He doesn't walk many hitters (although his high HBP rates can counter that) and gives up very few singles, so with good defensive support, he can still give up his share of doubles with minimal damage. I can't project whether he will improve over 2005 numbers (because two seasons do not make a trend), but I think he's still a very useful pitcher on this staff.