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Baseball’s New Hidden Ball Trick

A look at Major League pitchers who changed or elevated their career trajectory by hiding the baseball better than others.

MLB: Detroit Tigers at Chicago White Sox Mike Dinovo-USA TODAY Sports

One of my absolutely favorite things about baseball is all of the smaller nuances of the game itself. I’ve already made my feeling about swing aesthetics fairly well-known with my word-vomity piece on some of the more gorgeous swings at the Major League level. While I don’t possess the same love for pitching mechanics as I do for the hitters, I do very much enjoy the psychological element that occurs on the bump.

Deeply rooted in that psychological side is the idea of deception. Many pitchers can operate without it. They can step on the mound, huck high 90s, buckle a hitter’s knees, and walk back to the dugout. But some haven’t been as fortunate. Despite possessing good enough stuff in their arsenal, some hurlers have had to find other ways to thrive. And one of those ways that don’t involve the use of white cleats to mildly distract an opposing hitter is the concept of hiding the ball as part as their delivery.

There’s a number of pitchers that have adopted such a strategy in order to either elevate their game or change their career trajectory entirely. Like the hitting aesthetics column, perhaps this becomes a multi-part deal, but for right now I’d like to focus on just a couple that are among the most notable when it comes to a shift in performance and/or perception.

And that really starts with Lucas Giolito.

Giolito is notable because he had the pedigree of a premier pitching prospect. But in his brief time with the Washington Nationals and his early run with the Chicago White Sox, but he was never able to put it together in the way that might be expected with a prospect of his caliber. Across 32 starts in 2018, his K/9 sat under seven, he walked 4.67 per nine, and posted an ERA over six (FIP was over five). Here’s what his delivery looked like in 2018:

Lucas Giolito 2018 Delivery
Original Video via Baseball Savant

It’s pretty clear what’s happening here in this shot that he gives up to Jorge Soler. Arm comes way back out and way over the top. The transition from 2018 to 2019 is where we saw the mechanical change take place for Giolito. With it, he not only elevated his statistical output, but demonstrated almost an entire change in fortune as a result. He took his delivery from that to this:

Giolito 2020 Mechanics
Original Video via Baseball Savant

It’s the tuck behind the head for me. By maintaining his hand up behind his head, Giolito has been able to be that much more deceptive. And for a starter that relies primarily on two pitches, it’s been wildly effective. It allows him to not only keep the hitter off balance in regard to what type of pitch is going, but also the location of the pitch itself. Giolito is known for locating the change up in the zone, which is a fairly unique trait among starters. Such a trend likely could not have happened had it not been for the change in mechanics.

I mentioned the idea that Giolito changed his career trajectory. Here’s a look at the numbers prior to the change and then what transpired after:

Giolito Before & After

 2017-18 2019-21
 2017-18 2019-21
ERA 4.26 3.75
FIP 5.25 3.65
WHIP 1.22 1.1
K% 17.6 31.8
BB% 9.2 9.3
Total fWAR 0.4 7.7

It’s notable that Gio’s numbers are a little skewed by the dates I showed here. His output before the mechanical changes is boosted by a strong seven starts in 2017, while his post-mechanical changes looks a bit worse than it should because of a slow start to 2021. Regardless, it’s a fairly significant change for a guy who once appeared destined for bust status, but now registers as one of the more successful, and generally more fun, starters to watch throughout the game.

But Giolito isn’t the only one, of course. He might be the most well-known, just because of what the mechanical change has meant for him and his career. And his method of hiding the ball is specific to keeping that throwing hand behind his head for the duration of the delivery.

Joe Musgrove goes about things a little bit differently, while largely accomplishing the same thing. Musgrove wasn’t necessarily in the same situation as Giolito. While he’s been able to elevate his game, he wasn’t in the dire straits that the former National Giolito was. He was a mid-rotation starter who has burst onto the scene as an upper tier pitcher in his first season in San Diego.

Much of that can be attributed to his increase in deception. Here’s Musgrove’s delivery while with Pittsburgh:

Musgrove Pirates Pitching mechanics
Original Video via Baseball Savant

And here it is in San Diego:

Joe Musgrove San Diego mechanics
Original Video via Baseball Savant

This shift in mechanics is interesting because it isn’t nearly as noticeable or as distinct as Giolito’s. And Musgrove’s stuff already played extremely well. He just made a few subtle changes here, including just barely holding the ball behind his leg a little more, and maintaining a more upright delivery, which allows him to hide the ball just a split second longer than he otherwise would. That bend in the wrist really drives it home. It almost looks like he’s just going up and hucking, not looking nearly as calculated as he ultimately is.

There are other elements of Musgrove’s breakout. Increased fastball velocity and the infusion of the cutter have contributed. But we can’t understate the importance of concealment of his pitches, either. Mike Petriello has a nice writeup of it here and is far more intelligent than I. In any case, the outcome has resulted in the best numbers of Musgrove’s career to date, including a K% over 34.7, a 2.47 ERA, and 2.88 FIP.

Another who I’ve always enjoyed watching purely out of this concept is Zach Plesac. In another unique case, Plesac has always had a pretty short delivery—a contrast to Giolito who started long and got short. Video doesn’t do it justice, so here’s some stills, the first coming from 2019:

Plesac 2019 Delivery
Via Baseball Savant

Again, it’s short, but you can still see the ball out there on the backend. In more contrast to his AL Central counterpart, instead of making the change that Giolito made, where he tucks behind the head, Plesac utilizes his body for the bulk of his concealment:

Plesac 2021
via Baseball Savant

It’s a really cool, subtle change. In 2020, Plesac moved his ERA from 3.81 to 2.28 and his K% from 18.5 percent to 27.7 percent. Not bad for a guy who doesn’t have elite stuff. He also dropped his Hard% against by seven percent, down to 31.0. And it really speaks to what’s so extraordinary about this type of trend. It can come in the form of something rather significant, like with Giolito, or manifest itself as something much smaller and more subtle, in the case of both Musgrove and Plesac.

It’s not as if it’s always a sudden change in mechanics with this type of thing, either. Kyle Hendricks has been a master of ball concealment since he broke onto the scene with the Chicago Cubs. It’s why he’s been, rather quietly, one of baseball’s steadiest starting pitchers despite very rarely surpassing 90 MPH on the fastball. You don’t know if you’re getting the soft fastball or the nasty change.

You could make the argument that this is how Chris Bassitt has turned himself into one of the best starters in baseball over the past couple of seasons after turning 30. Bassitt uses the plant leg, then the drive leg, then his ass, and then his head while delivering one of the longest, goofiest deliveries you’ll see. But it works! Even if it doesn’t conceal quite as much, that length certainly speaks to the deception we’re talking about:

Chris Bassitt delivery
Original Video via Baseball Savant

I’ll choke on vomit as I write this next sentence, but Trevor Bauer has always been really great at this as well. He’s got the short arm path and uses his drive leg for further concealment. Somewhat obviously, Bauer’s leap to the top of the charts among starters can be attributed to other things that have allowed him to massively increase his spin rates, but even before he was elite, he was still wildly effective in managing to hide the baseball as part of his delivery.

In the interest of being economical with my words here, those are the arms at which I’ll leave it for now. There are starters that don’t need to do this. They can survive off stuff and movement and velocity. But for some, it’s either changed their career path entirely, in Giolito’s case, or elevated them from a mid-level arm to the front of their respective rotation. And there’s no one way to do it. Each example provided here did it in a very different way, but it all boils down to the same idea: deceive the hitter in every way possible.


Randy Holt is a contributing writer for Beyond the Box Score. You can follow him on Twitter @RandyHolt42.