This is a numbers post, but it's short, so hopefully it isn't too much. I just wanted to make sure we kept going with Felix Week.
All of the numbers contained herein were posted by Felix Hernandez against right-handed hitters. The first selection I'm going to show you is Felix's GB/FB against righties by year - that is, his ratio of groundballs to fly balls allowed.
You see a very, very steep dropoff between the 2007 and 2008 seasons. Because groundball rate is one of those numbers that stabilizes quickly, what this strongly suggests is that, in 2008, Felix started pitching to righties differently than he had before.
Now what I'm going to show you is Felix's strikeout rate against righties by year, beginning in 2008:
Here you see a pretty substantial increase between the 2008 and 2009 seasons. Because strikeout rate is another one of those numbers that stabilizes quickly, what this strongly suggests is that, in 2009, Felix started pitching to righties differently than he had in 2008.
Unfortunately, because of some issues with historical PITCHfx data, it's difficult to identify what changes Felix may have made. I can tell you that he's thrown more offspeed stuff to righties over the past two seasons than he did in 2008, but that doesn't mean a whole lot on its own. This post though, isn't about offering an explanation. Rather, I just think it's pretty cool that we can identify two points at which Felix appears to have made a change to his approach. Felix may have some stubbornness in his bones, but make no mistake; he hasn't been too proud to try different things, and he's better for it.