Yesterday, the Colorado Rockies traded right-hander Eddie Butler to the Chicago Cubs in exchange for a modestly promising relief prospect (James Farris) and the 28th international bonus slot.

Even as recently as last year, the notion of such a move would have seemed improbable. Butler appeared twice — as recently as 2015 — on Baseball America’s top-100 prospects list. The Rockies’ rotation, meanwhile, has been quite poor, producing the second-lowest collective WAR in the majors over the last five years. They haven’t been a club, in other words, that had the luxury of giving up on a promising young pitcher.

But Colorado’s rotation has improved rapidly, while Butler’s stock has declined just as quickly. In the end, general manager Jeff Bridich concluded there wasn’t space on the roster for Eddie Butler. He made a deal.

But this isn’t just a late-January transaction that ought to be forgotten. Because Butler has shown promise. Let’s instead follow his story up to this point. He deserves it after toiling in Coors for so long, and it might provide us a glimpse of his future.

The Virginia native was originally selected out of high school by the Texas Rangers — in the 35th round — in 2009, but he didn’t sign. He appeared on the national scene more forcefully after some time playing at Radford University for the Highlanders. True to form — there can be only one, after all — Butler was drafted in the first round and signed for $1 million with the Rockies.

He tore through the minors on the back of 97 mph gas and a devastating changeup. By the end of second year in the organization, he was in Double-A with an ERA under one. I want to point out the changeup, though. This changeup.

That’s a beautiful righty-on-righty changeup with devastating fade and drop from the 2013 Futures Game. We should remember those times, and that changeup, because it was sometime in 2014 that things began to go wrong. Maybe it was altitude, maybe it was too much of a focus on contact, but even his mid-3.00s ERA in Double-A in 2014 showed signs of trouble. His strikeout rate was gone, at least.

Then began the fits and starts that led to Butler’s current major-league record: 159.1 innings of an ERA over 6.00 on the back of poor strikeout rates and middling walk rates and very large home-run rates. It was sometime in that three-year period that I talked to Adam Ottavino, who pointed out that Butler just needed to find one more pitch to make it all work. Because of that changeup. And that velocity.

Something weird happened along the way, though. It can probably be most expressed in one easy table. Here is how often Butler has used his non-fastballs over the last three years.

Eddie Butler’s Pitching Mix Over Time Changeup Slider Curve 2014 22% 13% 1% 2015 15% 14% 6% 2016 6% 26% 8%

The results of each pitch tell the same story.

Eddie Butler’s Whiffs Over Time Changeup Slider Curve 2014 9.3% 9.4% 0.0% 2015 7.7% 13.7% 6.8% 2016 6.8% 14.3% 8.4% Swinging strike rate per pitch type per PITCHF/x

He found a new pitch! He lost the old pitch.

It looks like mechanics might tell some of the story. Butler used to release from a lower angle and get more drop on his changeup. Except that we’re comparing a few pitches in a Futures Game in 2013 to the rest of his career, which has been more over the top and with less drop. Let’s look at a 2016 delivery, and compare it to above, to see if it’s obvious that he’s changed his mechanics.

The release point looks higher here, and the changeup certainly doesn’t look the same. It’s fair to wonder if he can get it back, because the movement on it now only works if he pairs it with the four-seam. The change only has about an inch and a half more drop than the sinker, less fade, and only 6 mph of velocity gap. As he’s increased his sinker usage, he’s had fewer opportunities to pair the change with the four-seam, and the pitch hasn’t worked as well.

The good news is that he’s begun to harness the slider — it’s gone for a ball less and less often every year — and the highlights for that pitch are all over his MLB.com video page.

That’s a good pitch. He’s still throwing 93. The sinker has decent outcomes (55% grounders, 5% whiffs, both above average). He’s found a slider. That’s the now for Eddie Butler, and it’s more exciting than his results were last year.

The future? If it works out for him, and for the Cubs, who could use starting-pitching depth behind the six they’ll have in the majors, it’ll have more to do with his past than his present. He’ll find that changeup again, and he’ll find that promise that once made him a first-round pick and a Futures Game GIF monster.