Johnny Cueto of the Cincinnati Reds throws a very unusual change up. The uniqueness of the pitch stems from the spin he imparts to the ball. The following graph shows the relationship between the spin on his fastball and the spin on his change:
Notice that there is much overlap between the fastball and the change. That's good, as a pitcher want his change to look as much like his fastball as possible. What's different is that Cueto's change breaks farther away from his pitching hand than his fastball, in this case, away from a right-handed batter. If you look at most pitchers, the change up is identifiable by the speed and the bigger break toward the pitcher's throwing hand.
The type of movement seen in this change up suggests a slider, but Johnny throws a very good one of those:
The slider exhibits the spin that moves it away from Cueto's throwing arm. There still is some overlap with the change up, however.
Cueto throws his change the least, and it is also his least productive pitch. He records weighted On Base Averages (wOBA) of .167 on his slider, .275 on his fastball and .291 on his change. Those are all very good, but it's clear he gets much better results on his slider, which is why he throws it 2.5 times more than his change.
Given the spin of the pitch and batters ability to hit it, I wonder if his change ups are really poorly thrown sliders. A slider that didn't move much would explain why batters get more offense out of the pitch.