The awesome gets awesomer, as FanGraphs introduces some new stats including pitcher discipline metrics (basically, the same swing/zone/contact stats they already had for hitters but this time for pitchers). Using these new stats, we can see that Johan Santana had his worst season, at least since 2005 (the discipline stats only go back that far), in a lot of these areas.
|2005||69.1 %||30.2 %||72.2 %||53.7 %||50.7 %||81.9 %||74.2 %||55.9 %||3335|
|2006||65.4 %||30.1 %||71.6 %||53.0 %||50.3 %||83.1 %||74.8 %||55.3 %||3450|
|2007||65.4 %||28.2 %||72.6 %||52.6 %||51.8 %||80.0 %||73.2 %||54.9 %||3345|
|2008||63.8 %||26.8 %||69.2 %||50.0 %||59.8 %||82.5 %||77.0 %||54.7 %||3598|
Santana's first strike % (F-Strike%) was worse than it ever has been. Ditto his swing rate at balls outside the strike zone (O-Swing%). And his swings within the strike zone (Z-Swing%). It follows, then, that his overall swing rate (Swing%), the aggregate of those last two, is also the worst since 2005.
The most dramatic point of information here is Santana's contact rate outside the strike zone (O-Contact%), which increased from 51.8% in 2007 to 59.8% in 2008. This means that Santana got far fewer swing-and-misses in 2008 than he ever had before. His overall contact rate (Contact%) jumped from 73.2% to 77.0%, which would doubtless explain his alarming drop in strikeout rate this past season (9.66 to 7.91).
I don't have enough information right now to know if the increased contact rate is an obvious sign of onset regression, or if it's something that fluctuates to some degree from year to year (as Jake Peavy's has), and that maybe with a little better luck Santana's strikeout rate will more closely resemble his career mark in 2009.
It's something to keep an eye on, for sure.
EDIT: As Larry points out via email, a decrease in Z-Swing% is probably a *good* thing, since contact rate within the strike zone is generally very high.