Rondon has been close to this list in recent years and his progress with his slider in 2012 finally vaults him to the top. At all three stops in 2012, Rondon regularly showed a legit plus slider and occasionally mixed in a filthy one that made hitters look silly. He still needs additional consistency with the pitch, but the progress he has made over the last two or three years has been impressive.
Some scouts believe Crosby's curveball is the best breaking ball in the system, but more thought it was a half grade behind Rondon's slider. Crosby's curveball can be a true hammer at times but his arm action isn't ideal for consistency with the pitch.
Following the 2011 season, Luis Marte's curveball topped this list. He still has a dirty curve but the consistency was lacking in 2012, causing him to fall a few slots. Even without the consistency he displayed in 2011, Marte's breaker can still miss plenty of bats.
Will Clinard and Jake Thompson are both new additions to the Tigers system. Clinard has been lauded for his cutter that is downright nasty, and Thompson shows a plus slider on occasion, though he lacks consistency at this time.
Ferrell and Ortega were both close to the back end of the list, earning high marks for their curveball and slider, respectively. Ferrell's curveball gets a little slurvy at times but typically shows good shape and sharp bite. Ortega's slider is a short breaker with tight spin and sharp movement.
Belisario sat in this same position last year and is joined by Burgos as having the best breaking balls of the Tigers prospects yet to come stateside. The Tigers noted that Belisario made progress with the consistency of his curveball during Liga Paralela, showing more regularly as an above-average pitch, similar to Burgos' breaker.
The three lefties, Burgos, John and Rogers will all flash an above-average curveball on occasion and could get there regularly as they mature in the professional game. Heckaman relies on a cutter that isn't in the class of Will Clinard's but is a nice pitch. Slade Smith is a sinker-slider type with an average to solid-average slider that gets plenty of ground balls.