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Mound Visit: Musgrove’s fastball lagging ☕

Joe Musgrove - MATT SUNDAY / DKPS

STATE COLLEGE, Pa. — The trouble began for Joe Musgrove, tonight's scheduled starter against the Brewers at PNC Parkon May 3.

The scene began in the top of the second inning with the Athletics batting. A Jung Ho Kang error on a semi-routine grounder had put Khris Davis on base. He would eventually come around to score, with the Bay Area club still enjoying loaded bases alongside zero outs.

It was then that a nondescript catcher by the name of Josh Phegley set about his career day -- he would end the game with eight runs batted in -- at the plate. His bases-clearing double jolted observers who had watched Musgrove cruise to a sparkling 1.54 ERA for the month of April. His previous performance had made believers out of many, and now those converts faced their first taste of doubt.

From that date forward, Musgrove largely struggled, save for a gem of a start against the Diamondbacks followed by a quality start against the Padres. Still, he left May with an inflated 8.10 ERA on the backs of a .302/.364/.524 slash line (that's Batting Average/On Base Percentage/Slugging Percentage) against him. He struck out 20 and walked 12 in 30 total innings.

Musgrove has always had a wide variety of pitches. Technically speaking, he has four variations of a fastball, three of those being the standard four and two-seam varieties to go along with a cut version. He can also throw a special 'one-seam fastball' at times, though he throws it far, far less than he did during this time in Houston (and even then he did not throw it very much at all).

These, of course, served as ample table setters for his slider and changeup, both of which were very sturdy pitches in the season's early going, in addition to setting up his curveball, which makes a cameo here and there.

As the calendar turned to May, his pitch selection changed considerably:

[caption id="attachment_837283" align="aligncenter" width="500"] Musgrove pitch usage, month over month[/caption]

Along with a 6.3 percent jump in four-seam usage, the slider's usage has been bumped down slightly. This is a good time to note that judging pitch usage on its own merits is often misleading. Game situations often dictate that usage. If a pitcher who relies on fastballs finds himself in more fastball counts, more fastballs will be seen. If a pitcher with a good breaking ball -- and Musgrove falls into this bucket with his slider -- finds himself ahead in the count, you'll see more breaking balls. This particular aspect of pitching analysis is far from advanced.

No matter how he arrived there, Musgrove threw considerably more four-seamers in May. And the pitch faltered.

[caption id="attachment_837300" align="aligncenter" width="640"] Musgrove's four-seam peripherals, month over month[/caption]

Not only did Musgrove's four-seamer lose its mojo by way of harder contact against, but the contact was more frequent also:

[caption id="attachment_837302" align="aligncenter" width="640"] Rolling contact rate on all of Joe Musgrove's pitches[/caption]

If we continue to drill down on the four-seam fastball, we can see a few oddities pop up. First, a look at the location on these pitches:

[caption id="attachment_837304" align="aligncenter" width="640"] Musgrove's four-seam heatmaps, month over month[/caption]

Although it may appear as if Musgrove is catching more of the heart of the plate than he should, this is a little misleading. The chart from April shows a pitcher who can locate the fastball on both sides of the plate, while keeping it away from lefties and righties. The May data shows much less control -- notice all of the yellow, all over the plate -- with plenty of action in the sweet spots.

This sudden change, again, can be explained away by game situation to a degree. But there has also been a slight mechanical quirk that has popped up with Big Joe:

[caption id="attachment_837307" align="aligncenter" width="640"] Musgrove's four-seam release points, month over month[/caption]

That is a map of all of Musgrove's release points on his four-seam fastball, separated by month. While the difference may be small, notice how much wider of a range the pitch had in May. Believe it or not, this bit of difference can play a huge part in deciding if Musgrove can hit a spot, or if the pitch can sail into dangerous territory.

The minutiae of mechanics is on display in the video below. On the left, a four-seam groundout from April. On the right, a strong double off of the four-seamer in May:

The change is almost minuscule, and, I must confess, required considerable pausing, rewinding, playing, and then pausing some more before I could see it. The "tell" for me came in the follow through. On the right, Musgrove is a bit more open at the end of his motion, reinforcing the notion that his arm is coming over the top at an inconsistent point:

This all may seem so minute to make much of a difference -- infinitesimal, even -- yet small changes in mechanics or delivery such as this is enough to throw any pitch out of whack.

And when a pitch is relied upon as much as Musgrove's four-seamer, the cumulative effect can be substantial.

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