One of the weird things I've noticed about Butler is that he's changed how he pitches, but not how he was supposed to change. When he was a prospect, he used to pitch from a lower angle and he got a lot more drop on his pitches, as Eno Sarris showed when we traded for him: http://www.fangraphs.com/blogs/eddie-butler-then-now-and-in-the-future/ The Rockies tried to change him and it really messed him up. When we got him, Bosio was supposed to get him back to his natural pitching motion. https://www.si.com/mlb/2017/02/21/chicago-cubs-chris-bosio-pitching-lab Essentially, this is what happened with Arrieta. That's why he was supposed to be Arrieta 2.0. His previous club was messing with him to fit their organizational preferences. Bosio would let him be himself and he'd go back to what made him good. Then, there was this note in a Fangraphs piece, when he was in Iowa: http://www.fangraphs.com/blogs/sunday-notes-whitleys-cattle-cubs-butler-gausmans-analogy-yard-goats-more/ Going downhill is the exact opposite of what he was supposed to be doing. That's what the Rockies were having him do. He was supposed to be going back to his natural, lower release point. And if you look at his release points, he is going more downhill. His vertical release point is way up from where it was even in Colorado. He's pretty much straight-over-the-top now. http://www.brooksbaseball.net/velo.php?player=572750&b_hand=-1&time=year&minmax=ci&var=z0&s_type=2&startDate=03/30/2007&endDate=06/06/2017&gFilt=&pFilt=FA|SI|FC|SL|CU|CS|KN|CH|FS|SB If you look at it game-by-game, he was all over the place the last couple of years. He may have been going up from where he was when he was a prospect, but it was constantly fluctuating; nothing was repeatable. At least this year, it's been more stable. It seems like his delivery is more repeatable. And the gap between his release points on different pitches has shrunk. This delivery may help him to better disguise his off-speed stuff from his fastballs. http://www.brooksbaseball.net/velo.php?player=572750&b_hand=-1&gFilt=&pFilt=FA|SI|FC|SL|CU|CS|KN|CH|FS|SB&time=game&minmax=ci&var=z0&s_type=2&startDate=03/30/2007&endDate=06/06/2017 But, this isn't the Arrieta process. In fact, it's pretty much the exact opposite of it.