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In my humblest of opinions, the most exciting pitch in baseball (regardless of level, but particularly the MLB level) is the changeup. If you have read any of my previous articles or have followed me on Twitter for virtually any part of a season, this should already be abundantly clear. Sure, a changeup does not have the movement of a breaking ball or the velocity to light up a radar gun, but a change's ability to make really good professional hitters look silly, often through deception, truly makes the pitch an underappreciated baseball treasure.
In case you missed them, I have already written two "repertoires in review" posts: one on the fourseam fastball and the other on the sinker. Predictably, Trevor Rosenthal ran away with the staff's best fourseamer, and as I had hoped, Carlos Martinez comfortably leads the way when it comes to sinkers. Given the candidates I am considering for the best changeup on staff, I sincerely believe there will be much more parity in today's poll results.
The basics (using 2015 PitchF/x data unless otherwise indicated)
| Pitcher | CH Frequency | CH Velocity (MPH) | FB Velocity | Velo. Difference (CH - FB) |
| Tim Cooney | 22.62% | 82.83 | 90.27 | -7.44 |
| Jaime Garcia | 15.02% | 83.77 | 91.02 | -7.25 |
| Marco Gonzales (2014) | 25.80% | 79.15 | 90.44 | -11.29 |
| Carlos Martinez | 17.18% | 87.69 | 96.53 | -8.84 |
| Trevor Rosenthal | 16.50% | 88.57 | 98.55 | -9.98 |
| Michael Wacha | 16.37% | 87.29 | 95.01 | -7.72 |
In a vacuum, changeup velocity does not tell us much, but rather, one must consider its velocity relative to a given pitcher's fastballs (fourseamer, sinker, or in some cases, both). Whether you choose to look for an 8-12 MPH difference between fastball and changeup velocity or an 8-12% difference, it does not really matter considering we are talking about pitchers throwing in the low to upper 90's. Each pitcher considered in this post meets (or comes very close to meeting, at least) the desired velocity difference between the two pitches.
2015 dragless horizontal movement (in inches, courtesy of BrooksBaseball.net)
Remember: Regarding horizontal movement, a positive value means arm-side movement for left-handed pitchers, while a negative value means arm-side movement for right-handed pitchers.
| Pitcher | Changeup | Fourseamer | Sinker |
| Cooney | 14.92 | 7.60 | 15.13 |
| Garcia | 13.57 | 4.27 | 11.43 |
| Gonzales (2014) | 16.19 | 11.75 | N/A |
| Martinez | -13.61 | -6.58 | -12.99 |
| Rosenthal | -10.83 | -7.28 | N/A |
| Wacha | -9.56 | -5.84 | N/A |
Nearly as important as the 8-12 MPH (or percent, if that's what you prefer) difference in velocity between the fastball and changeup is each pitch's given horizontal movement. Out of the hand, and on its way to the catcher's mitt, an ideal changeup follows as similar a path as the fastball as possible, as this is a major component to the pitch's deception.
For those pitchers that equally utilize both a fourseamer and a sinker, it is best to have the changeup's movement somewhere in the middle of the movement of the two fastballs, but is often considerably closer to the sinker (which, given the grip and velocity of the pitch, makes sense). Those pitchers without a sinker (Gonzales, Rosenthal, and Wacha) have to work slightly harder for consistent effectiveness, but it's not impossible, especially if they are able to match release points and arm speed.
2015 pertinent outcomes
| Pitcher | Whiffs/Swing | HR/FB |
| Cooney | 42.31% | 8.33% |
| Garcia | 35.61% | 5.88% |
| Gonzales (2014) | 46.46% | 7.69% |
| Martinez | 42.80% | 12.50% |
| Rosenthal | 44.55% | 0.00% |
| Wacha | 34.01% | 14.29% |
A note regarding Martinez's 12.50% HR/FB ratio: In 2015, only 6.94% of balls in play against his changeup actually went for fly balls (63.89% ground balls), so the high HR/FB% is slightly misleading.
2015 results
| Pitcher | AB | K | BB | BA | ISO |
| Cooney | 26 | 8 | 3 | .154 | .154 |
| Garcia | 66 | 20 | 4 | .212 | .061 |
| Gonzales | 47 | 13 | 6 | .255 | .106 |
| Martinez | 122 | 49 | 14 | .148 | .098 |
| Rosenthal | 53 | 20 | 4 | .113 | .000 |
| Wacha | 163 | 58 | 5 | .209 | .172 |
Given that we are dealing with small sample sizes (i.e. Cooney has thrown 107 MLB changeups), it is nearly impossible to arrive at much from the two tables above (honestly, velocity and pitch movement are much more important), but a few components, whiffs/swing in particular, are definitely something worth considering before casting your final ballot. Also, while this is essentially a vote on data that occurred in the past, one cannot help but think about whether or not the pitcher will be able to replicate past performance. Gonzales was an effective pitcher in 2014, but after a lost season due to shoulder issues in 2015, will this affect his repertoire going forward? We will soon find out.
Unlike the first two posts of this series, I did my very best to not steer the reader one way or another up to this point. Frankly, we are fortunate to have a pitching staff full of really good changeups. I have my choice for the best changeup on staff (and after revisiting the data, it is much closer than one might think), but I want to hear from you...after you have looked through the data, read my general thoughts on the pitch, and watched each changeup in GIF form below.
Bonus GIF section
Cooney
Garcia (This one may take slightly longer to load, and for that, I apologize) 
Gonzales
Martinez
Rosenthal
Wacha
As usual, credit to BrooksBaseball.net for the data and The Pitcher List/@mstreeter06 for the GIFs used in this post.