Matt Bowman's arm is falling off

When Mike Matheny was faced with his first bullpen decision of 2018, he opted for the familiar right arm of Matt Bowman for the 135th time.

Bowman’s 2018 debut didn’t go as planned. He gave up three runs and retired only one of the five hitters he faced on a sac bunt by Syndergaard. Known as groundball specialist, Bowman gave up three singles, all on balls in the air between 15 and 17 degrees. He single handledly dropped the Cardinals win expectancy from about 45% to 5%.

Last week in a Prospects After Dark periscope, Kyle Reis noted that Bowman appeared to be compensating for some discomfort in his throwing motion. Today, after watching Bowman look terrible, Kyle again chimed in:

“It doesn’t look like [Bowman] is getting extension on the backside. It’s like he’s holding his arm closer to his body as if to cradle it.”

I usually don't trust the eye test. It's really hard for the eye test to pick up subtle differences at high speeds in large samples spread out over 162 games. However, I've come to trust Kyle's eyes more than most, including my own, and I wondered if there was something more to what he was seeing.

One easy way to detect potential arm discomfort is velocity. Here’s how Bowman's fastball velocity has fared over last two years:

The former Rule 5 draftee began the 2016 season averaging about 92.5 mph on fastballs. In July 2016, he was near 93.5 mph. By the end of 2017, he was below 91 mph. On Thursday, his fastballs averaged 91.4 mph. Not surprising, and not good.

While velocity tells at least part of the story, Kyle’s comment prompted me to take a deeper look into Matt Bowman’s Statcast data. Among the many things Statcast tracks is release point extension. Anyone who’s tried to throw with a sore arm knows that you don’t keep the same mechanics and, often, you cut your motion short.

There were 221 pitchers who threw at least 100 fastballs in both the first half of 2016 and again in the second half of 2017. I ranked them by their change in release extension from the first period to the second. Here is the bottom of that leaderboard:

Matt Bowman. Dead last! No one lost more extension from the first half of ’16 to the end of ’17 as Matt Bowman.

To go along with significantly less extension, and maybe as a product of that erosion, Bowman induced whiffs on only 15.9% of swings against his fastball in the second half of 2017, compared to 24.5% in the first half of 2016. His wOBA allowed on fastballs shot up to .339 from .292. And he went from a ground ball machine to, well, not:

The release extension is plotted along the x-axis, and change in launch angle allowed along the y-axis. You don’t want to be on the left side of this graph, and you don’t want to be at the top. Matt Bowman is both, and no one else is even in his neighborhood.

This is extreme. Really, it’s terrifying. From a performance perspective, it’s terrifying because Matt Bowman never really had any great qualities outside of his ability to induce ground balls. He's lost his ability to induce ground balls. From a health perspective, I can’t imagine the discomfort that leads to a pitcher losing more than six inches of extension.

Given Mike Matheny’s history of overusing relievers, Matt Bowman’s abuse is unlikely to end anytime soon. As one of “Mike’s Guys,” it will probably take at least a month or two of poor performance for Matheny to steer away from him. In the meantime, we will likely see Bowman run out there in important situations while better options sit unused.

This is to say nothing ill of Bowman – he is just trying to do his job as dictated by the manager to the best of his ability. It’s the manager who needs to realize his pattern of overuse to and back off. In that regard, 2018 isn’t off to an auspicious start.

Photo credit: Kat Allen. Follow her @kat_allen311

Credit to FanGraphs and Baseball Savant for their contributions to this post.