One of the things I found most interesting was the discussion of what happened with Manny Parra last season. He described Bryan Price giving him a project to look into Manny Parra's pitches and mechanics, and try to find a way to help him improve. One of the things he reported back was that Parra's curveball was really inconsistent, and that really hurt his performance. So, they encouraged him to drop it in favor of a slider.
Not that I doubted it, but I wanted to look at his pitchf/x profiles. Here are Parra's 2009-2012 pitches:
You can see him grade out as having a fastball, a split finger, and that curveball. Note that each dot above is an individual month during that time period, not an individual pitch.
Here are his 2013 pitches:
And there's the slider! Note that the y-axis changed here. The curveball came in around 77mph and had a spin axis over 300 degrees, whereas the new slider comes in at 83 or so with a sub-300 degree spin, so it's clearly a new pitch. Just to show this more clearly, here are his 2012-2013 pitches:
All of the sliders were thrown in 2013, and all of the curveballs were thrown in 2012.
Another interesting thing: it wasn't an occasional-use pitch for him. In 2013, he threw his slider 41% of the time, compared to just 18% for his curve in 2012.
Looking at his stats:
The biggest change of substance in his record looks to be a dramatic improvement in his walk rate. He also posted a career-best BABIP, though it was still above league-average (last year that was 0.297). I think that both of those things could potentially be attributed to swapping his curve for a controllable, effective slider. Now he has a pitch that he can throw for strikes, and can induce strikes (45% of swings at the slider were whiffs last year). And if hitters are whiffing at the pitch, they're going to be making weaker contact with it when they do strike true. Finally, if they have to beware of his breaking ball, they can't sit on his fastball and sinker.
Kudos to Parra, Mark Jenkins, and Bryan Price for figuring this out! I love seeing pitchers making real, measurable changes in their approach that result in such dramatic performance improvements. Here's hoping he can do it again this year!