The Jonathan Sanchez narrative states that he's gradually developed and matured into a top arm in the National League. ERA seems to confirm that, though FIP and xFIP tell us otherwise:That essentially debunks the whole "Sanchez has matured" theory, right? Somewhat.SIERA tells us a little more about Sanchez, because it adjusts for some of the flaws of FIP/xFIP. Here's where I think it's most applicable to Sanchez:Allows for the fact that a low fly-ball rate (and therefore, a low HR rate) is less useful to pitchers who strike out a lot of batters (e.g. Johan Santana's FIP tends to be higher than his ERA because the former treats all HR the same, even though Santana’s skill set portends this bombs allowed will usually be solo shots).From 2008-2010, Jonathan Sanchez's K/9 (9.40)...

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