My take on Arroyo?
His ERA has been driven by his BABIP both of which have dramatically improved with the significant improvement of the defense behind him. In other words, significant interaction between his performance and the Reds defense is a large reason why he's outperformed his peripherals so dramatically (i.e. his ERA has been better than his FIP would predict) over the last several seasons. Or to say it another way, put him in front of the Reds defense of 2006-2008 and his ERA would be much closer to his FIP.
Why do I argue this?
Here is a breakdown of Arroyo by year showing his ERA, FIP and BABIP. When the FIP-ERA is positive, it means his ERA was lower than his peripherals would predict (i.e. his ERA outperformed his FIP):
It's important to note that Arroyo's ERA has outperformed his FIP in 5 of the 6 seasons he's been a Red. But many would agree his 2006 ERA was an anomaly that was unsustainble. Certainly the magnitude of difference between his FIP and ERA spanning the 2009-2011 seasons would not have been expected based upon his prior performance or legitimately ascribed to a skillset. Realizing some may argue this point, below follow a few tables that hopefully demonstrate why one might make the above statement.Code:Arroyo Season ERA FIP FIP-ERA BABIP 2006 3.29 4.15 0.86 0.271 2007 4.23 4.57 0.34 0.309 2008 4.77 4.5 -0.27 0.314 2009 3.84 4.78 0.94 0.265 2010 3.88 4.61 0.73 0.239 2011 5.07 5.71 0.64 0.278
Here's the same breakdown for the Reds' pitching staff over the same years:
Here are the BABIP for the Reds staff and Arroyo for the two periods of his tenure as a Red (2006-2008 where the Reds had one of the worst defenses in the league and 2009-2011 where the Reds had one of the best defenses in the league):Code:Reds Season ERA FIP FIP-ERA BABIP 2006 4.51 4.63 0.12 0.31 2007 4.94 4.55 -0.39 0.31 2008 4.55 4.53 -0.02 0.312 2009 4.18 4.66 0.48 0.283 2010 4.01 4.18 0.17 0.288 2011 4.16 4.45 0.29 0.282
The data above indicates that for the period of 2009-2011 when Arroyo's ERA has significantly outperformed his FIP despite declining peripherals, the Red's staff as a whole has consistently outtperformed it's FIP as well. The third table suggests the reason why-the dramatically improved defense has driven a large part of this outcome. So he did not outperform his FIP independent of significant influence by his defense.Code:BABIP by defensive performance Reds Arroyo 2006-08 0.311 0.298 2009-11 0.284 0.261 Decrease -0.026 -0.037
So in other words, if the Reds were to pay market value for Arroyo's production over the last several seasons, they'd essentially be "paying double" for the cost associated with building their defense. This also can explain why Arroyo does not have a great deal of trade value despite his ERA's.
All of that said, a look at Arroyo as a Reds does seem to suggest he has outperformed his peripherals to a greater degree than can solely be explained by the impact of the defense behind him. So there may be room to poke at something interesting here, albeit a minor effect. However, when looking at his time as a Pirate and BoSock, he displayed no discernible ability to consistently outperform his peripherals.
The ultimate takehome? If they can get a legit arm for their rotation, they should. At least Arroyo should not be a rationale for preventing such a trade.