Looking more into this xFIP-ERA P Alan Busenitz-
since 2014 Angels starters have outperformed xFIP by .29 runs/game.
Weaver, Santiago, Tropeano, and Heaney have outperformed the most. Interestingly they are all fly ball guys.
Richards has also outperformed it being an extreme ground ball guy. Shoemaker being a 50/50 guy, has matched his ERA to his xFIP.
Since 2014 Twins starters have underperformed xFIP by .54 runs/game.
May (+1.52, 40.6% FB),
Nolasco (+1.21, 36.4% FB)
Duffey (+1.08, 28.6% FB)
Hughes (+.34, 40.4% FB)
Santana (-.56 runs/9. 36.7% FB)
Since 2014 the Angels have had the 3rd best defense, the Twins the 3rd worst. Roughly 100-150 runs separated them.
Actually between 2006-2013 the Marlins defense was pretty bad too, 4th worst.
Safe to say that a significant portion of Ricky's xFIP-ERA underperformance is defense-related IMO.