The 2015 changeups of Carlos Martinez, Trevor Rosenthal, and Michael Wacha

Thirty-nine games into the 2015 season, the pitching staff of the 26-13 St. Louis Cardinals has been terrific (2.79 ERA, 3.22 FIP). At present, three pitchers on staff (two starters, one reliever) achieve much of their success through the use of a plus changeup: Carlos Martinez, Trevor Rosenthal, and Michael Wacha. Tomorrow, another great changeup will join the staff when Jaime Garcia makes his 2015 debut against the New York Mets, and it is likely we will see another one later in the season when Marco Gonzales makes his return to the big league club.

Let's take an early look at the 2015 changeups of Martinez, Rosenthal, and Wacha. I realize the sample is pretty small for all three pitchers, especially Rosenthal, but this is a topic I plan on returning to multiple times throughout the season, given the fact that the changeup is my favorite pitch. If Garcia is able to stay healthy for more than a handful of starts, I can imagine he will be included in any future changeup articles.

Changeup movement

For a consistently successful, deceptive changeup, it is ideal to have it follow a flight similar to the given pitcher's fastball, sinker, or at least in the general vicinity of the two in order to allow for effective use of "pitch tunneling." In Martinez's case, his changeup (which some prefer to classify as a screwball) predictably has more horizontal movement than both his sinker (-12.86 inches) and his fourseamer (-6.64 inches). This horizontal movement, combined with a significant amount of drop, makes it especially tough on hitters to make contact (as you will see below).

Next on the list in terms of horizontal movement is Rosenthal at -10.45 inches, nearly double the tailing action of his fourseamer (-5.95 inches). Given that Rosenthal does not have a sinker to mimic, it makes sense that his changeup has considerably more horizontal movement than his fourseamer. Recently, he has used a hard slider (89.43 MPH) more frequently, making his changeup an even more effective weapon, as the difference in horizontal movement between the two averages out to be 15.87 inches (or 1.32 (!) feet), despite following a pretty similar pitch tunnel out of the hand. Here is Drew Silva's in-depth thoughts on the pitch:

Trevor Rosenthal's changeup ...

— Drew Silva (@drewsilv) May 14, 2015

I don't intentionally mean to make Wacha's changeup, a very good pitch, sound like an afterthought, but there are three factors at play here. First, thus far in 2015, Wacha has used his cutter much more frequently (15.70%) than in previous seasons, and second, though the changeup has more movement than it did in 2013, it just does not appear to be his go-to "out pitch," as it was in 2013. Third, when comparing Wacha's 2015 changeup to Martinez's and Rosenthal's, in my opinion (please, share yours below), it is pretty clear that it comes in third, which, honestly, should not at all be seen as a slight to Wacha.

Changeup outcomes

A changeup gains its success through deception of the hitter. Out of the hand (similar vertical release points) and through the initial part of its ball flight to home, a hitter will be unable to distinguish between a fourseamer/sinker or changeup. Thus, when a hitter is timed up for a fastball but receives a changeup, the velocity difference (ideally 8 to 12 MPH) leads to weak contact or often no contact at all. Martinez and Rosenthal have the desired velocity difference between their fastball and changeup, and while close, Wacha is not quite there at 7.05 MPH. While Wacha threw his fastball harder in yesterday's game than he has all season, his changeup velocity increased as well, so there was no real change in the velocity difference between the two.

In terms of whiff/swing, Martinez is the highest of the three with roughly two whiffs in every five swings (40.91%). Martinez's foul/swing (also at 40.91%) makes the pitch even more impressive because it means that eight out of 10 swings against his changeup have a result other than a ball in play. That is one way to limit the damage of opposing hitters. Rosenthal's (whiff+foul)/swing is 64.28% and Wacha's 55.88%. While both of these percentages are very good, they are still much lower than Martinez's (81.82%).

Changeup results

It is nearly impossible to draw any conclusions from 40 at bats or fewer, but I figured this post would not be complete without the inclusion of a results table. Regarding Martinez, he has allowed only three hits on the changeup thus far, but two of them have been homers, leading to an ISO of .207. One of the home runs was by Anthony Rizzo of the Cubs, and upon further review, it appeared to be a hanger (middle vertical location), despite being located off the plate away. Like Martinez, Wacha has allowed two home runs on his changeup thus far in 2015, while Rosenthal has allowed only two hits, both falling in for mere singles. Due to sample size, this is as far as I am going to interpret this table.

Now, courtesy of The Pitcher List, here are three changeup GIFs for your viewing pleasure:

Martinez changeup GIF:

Full AB via BrooksBaseball

Rosenthal changeup GIF:

Full AB via BrooksBaseball

Wacha changeup GIF:

Full AB via BrooksBaseball

As usual, credit to @ThePitcherList for the GIFs (I strongly recommend checking out their wonderful website) and BrooksBaseball for PITCHf/x data.