A changeup is not a requirement for being an ace. Eno Sarris' piece on JABO has basically all the background info you need to know. Not-so-long story short, pitchers who throw the changeup a lot get injured less. Changeups offer a change of movement and speed. It helps reduce platoon splits. It's a good pitch.
There are a few pitchers who have seen fit to increase their changeup usage over the past few years, though. Three of the following four pitchers would qualify as "aces", though I'm not using anything other than a gut feeling to define "ace". The fourth is there as an interesting comparison. Chris Sale. Felix Hernandez. Zack Greinke. Jeremy Guthrie? Each one of the four has increased his changeup usage over the past 3 years, but not all of them have achieved the same results.
This simple Tableau viz compares the four players on usage and whiff rate, and hovering over the data points in the usage graph should show the velocity of the pitch as well. While all 4 have increased usage (and increased velocity), the whiff rates differ. Hernandez and Guthrie have fluctuated while Sale and Greinke have made a dangerous weapon devastating.
Whiffs don't tell the whole story, though. The following viz looks at horizontal movement, vertical movement, and GB% for each player.
Hernandez' GB% has increased each year, while the other guys' rates have fluctuated. There are fragments of explanations to be found for each player. First, note Guthrie's differences. Guthrie's usage has increased, but neither whiffs nor ground balls have increased. There is a fairly significant difference between Guthrie's changeup and everyone else's: vertical movement. The three aces all have roughly the same vertical movement, and there is a fair amount of it. Guthrie's change lacks the same vertical movement.
Hernandez gets the most whiffs and the most ground balls with his changeup. That's a scary combination. Hernandez' vertical movement appears to be favoring a higher changeup, but Hernandez is in fact locating the pitch more under the zone. That's not making it any easier to hit.
Sale and Greinke are showing a bit of a change regarding their release points. They are converging ever so slightly with their other pitches. Their other pitches are also pretty good, so if hitters can tell even less what's coming, that would help the changeup be more deceptive. All the other pitches would be more deceptive too.
As for Guthrie, who knows what's going to happen. Guthrie may have learned something from James Shields and his changeup, but Shields is about 99% likely to leave the Royals this year. Guthrie's changeup was a decent pitch last year, but if constant feedback from Shields was the reason behind it, there's no guarantee the pitch will be effective. There's no guarantee Shields had an influence on the effectiveness of the pitch anyway; Guthrie's 2014 changeup was similar to his 2012 changeup by whiffs and GB%. Shields wasn't with Guthrie in 2012.
Even among the guys who have great changeups, they don't always use them in quite the same ways. Just like guys without changeups can be successful, guys who use the changeup differently with different results can still be successful with it.
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All statistics courtesy of Brooks Baseball.
Kevin Ruprecht is an Editor of Beyond the Box Score. He also writes at Royals Review. You can follow him on Twitter at @KevinRuprecht.