Kyle brought up the interesting idea of looking at Tim Dillard, because he's a really rare case study: someone who has pitched in the big leagues like a normal pitcher, converted to a sidewinder, and then pitched in the big leagues again. I want to check out how much his stuff changed.
Dillard threw 14 1/3 innings for the Brewers back in 2008 and only 4 1/3 in 2009. He struck out 5 and walked 6 in his 2008 major league appearances, and walked 5 and struck out 1 in his brief 2009 stay in the majors. That was the story of Dillard, he looked to have good stuff and put up good basic numbers at AAA (11-7 record, 148 innings, 4.5 ERA as a starter in 08) and some wanted him brought up and bought into the starting rotation in '09. But his ratios were always pretty bad, and especially in 09, he had 3.9 K/9 and 3.2 BB/9, which is Suppan-esque, except for at AAA.
So the Brewers asked him to make a change, thinking there was little chance he'd see the majors as a conventional reliever. It seems to have paid off so far, as his stuff has looked good and he has been extremely tough on right-handers. There's pretty much no chance he'll ever be more than a righty specialist, but that's something that has value, and is something that Sean Green is not.
Before the transition, Dillard had a pretty big fastball. It averaged 92.9 in the bigs. He threw the straight fastball about 60% of the time, and splitting most of his remaining pitches between an 89 mph sinker and an 85 mph slider. He was your typical sinker/slider reliever in the Dan Kolb mold. But as nice as his stuff looked on paper, he didn't really fool anybody. Batters made contact with about 92% of the balls Dillard threw in the strike zone, and only swung at about 25% of the pitches Dillard put outside the zone. All this led to a swinging strike rate around 4%, which is well below the league average and the reason he was only able to strike out 6 batters in 20ish innings.
Dillard's still a sinker/slider guy now, but he brings the ball in from a different area code. His fastball now averages 84.8 mph, and he's thrown it a crazy 80 times out of 87 total pitches thrown. The coolest thing is that his fastball now has a lot more sinking action on it now than it did when he was an over the top sinkerballer. He's also thrown his slider 7 times, and it's a big sweeping one (no shock there) that averages 74.7.
Here's a side-by-side that I put together from TexasLeaguers comparing his release points. You're looking at this from Lucroy's (or Nieves) perspective.
Here's another image, comparing the view of his pitches from the side. Note the difference in where they start from, and how significantly the sidearm pitches rise and drop. I made a little mistake and put them in reverse order, the dates are at the top. The left is sidearm Tim, right is overhand Tim. If you can't see all of either of these images let me know and I'll try to fix it, and your best bet is to go up to the right sidebar and change the view to wide if you're on narrow.
The big news is what it's done for his results. Now batters have swung at 37% of pitches outside the zone compared to 25% before, and made contact with 36% of those out of the zone pitches, compared to the upper 80s before. On pitches in the zone, the number is about 80%, down from the low 90%s. Overall, he's thrown a lot more strikes, and batters have made a lot less contact (90% of total pitches swung at were hit somewhere before, now it's 65%) and his swinging strike rate has jumped from 4% to 16%.
All of these changes are subject to a lot of disclaimers. The main two are that Dillard has faced mainly righties, and might have been better before if he were treated that way, and that we're talking about under 7 innings and 90 pitches worth of data so far. That's like a guy coming up from AAA and making one start in which he strikes out the ballpark and us concluding that he's improved drastically. That's not what I'm doing, just pointing out the simple fact that velocity isn't necessarily equivalent to nasty stuff (Shaun Marcum should be one of the first sources for this claim). Dillard has retooled himself into something useful knowing full well that his radar gun readings would not be as pretty, which is something a lot of pitchers probably wouldn't do. It's been a pleasant surprise so far, and he can continue to be useful if he's shielded from facing any lefthanders.
Edit: If you click on either image it will take you to Photobucket where you should be able to see the entire thing.