Inspiration.
I feel disappointed. The Diamondbacks season will very likely fall short of the playoffs, largely because of serious injuries to pitchers. Why?
That question may never be definitively answered. Attempting to answer it might be a fool’s errand. One reason is that characteristics that make a pitcher effective may at the same time increase their chances of injury.
Let’s focus was on six Diamondbacks who pitched at least 5 innings during the regular season in 2025 and who were injured most seriously: Corbin Burnes (Tommy John surgery), Tommy Henry (Tommy John surgery), Justin Martinez (Tommy John surgery), Christian Mena (shoulder strain), Shelby Miller (forearm strain), and AJ Puk (Tommy John brace surgery). That focus means ignoring three pitchers: Jordan Montgomery (Tommy John surgery), Blake Walston (Tommy John surgery), and Drey Jameson (bone chip).
In the context of a non-expert Diamondbacks fan, I hoped to shed some light on things that could possibly be correlated to the injured pitchers (although correlation is different than causation). Further investigation could be worthwhile.
A big caveat is that the Diamondbacks should rely on their experts. I have great respect for those who develop expertise in their endeavors.
The difficulties were daunting. Read onward if you dare.
Ratio of Supinated Pitches to Pronated Pitches.
My understanding of supinated and pronated pitches follows:
Immediately prior to the release point, most pitches (fork ball is an exception) involve the hand and forearm rotating. Two directions of rotation are possible: supinated or pronated. After the pitch is released, if the palm is semi-upward that is a supinated pitch; if the palm is semi-down that is a pronated pitch.
The ratio of the two pitch types was estimated by first deciding whether each pitch type is typically supinated or pronated. Then, the total supinated pitches was divided by the total pronated pitches.
The following table provides my opinion of whether pitch types are typically supinated or typically pronated.
Various sources on the internet informed my opinion. Individual pitchers may have developed pitches that differ. References on kick changeups and pronated sliders follow in next paragraph.
The estimated ratio of supinated pitches to pronated pitches could be inaccurate by a significant amount because new pitches (with the opposite rotation) are added before Baseball Savant tracks them. Two examples follow:
- The kick changeup can be supinated instead of the usual pronated for changeups. The origins of the kick pitch were written about by Eno Sarris.
- The slider can be pronated instead of the usual supinated. This video provides insight.
So why care about supination?
“Over supination or supination maintained too late in the throwing motion is often catastrophic for throwing athletes. The only absolute in throwing mechanics is that once you start a throw you almost always end up finishing a throw. Excessive supination in the throwing motion will tell the brain that the throw needs to happen earlier which alters upper extremity sequencing, fulcruming, and positions the elbow in a less stable configuration.” —Jeff Mackey, September 2020
This season, as a team, the Diamondbacks’ ratio of .59 is the sixth smallest in the Majors. Despite the small ratio, three pitchers had high ratios. Two of the three were injured.
This season, the Diamondbacks pitchers with the highest ratios follow:
- Corbin Burnes, 8.65
- Tommy Henry, 1.83
- Jose Castillo, 1.60
Split Finger Changeups.
“The performance on splitters is so good that even if the injury risk was higher – and again, the evidence doesn’t really support that – there’s an incentive for fringe pitchers to take on that risk to get to higher performance that would allow them to have or sustain a big league career, as opposed to a lower-risk approach that keeps them in the Minors.” — Mike Petriello, January 2024
“The pitch-tracking era has changed what we call things, and there is a lot of grey area around what a changeup vs a splitter is… the splitter fell out of style, with fears of injury risk clouding the sunny excitement of its effectiveness.” — Josh Bookbinder, Feb 2024
This season, the Diamondbacks with the highest percentages of split finger changeups follow:
- Scott McGough, 31.6%
- Justin Martinez, 30.9%
- Shelby Miller, 26.9%
- Taylor Scott, 11.7%
Two of the four pitchers suffered injury. Shelby Miller suffered a strained forearm. Justin Martinez had Tommy John surgery. Was there a correlation? Because of Taylor Scott’s low arm angle, perhaps he was at less risk throwing split finger changeups.
Fastball Velocity.
An obvious correlation is throwing fastballs with a high velocity. This season, five of the six injured pitchers know what it means to pitch with an average fastball velocity over 95 MPH. Two injured pitchers had a drop in monthly average velocity, which is a known indicator of potential injury. For further insight, see this June of 2021 study which looked at trends before injuries occurred.
The following table shows the average fastball velocity (by month) for Corbin Burnes, Tommy Henry, and Brandon Pfaadt. They were included in the table because each of them experienced at least one 1-month drop in average fastball velocity.
Monthly average fastball velocity in MPH. Data from Baseball Savant.
The table shows Burnes and Henry may have experienced a drop in average fastball velocity before their injuries. In addition, as a fan I have concern about whether Pfaadt can avoid injury.
Summary.
The question of why the Diamondbacks pitchers were injured may never be answered. With the caveat of a non-expert fan looking at characteristics of the injured pitchers, the followed table shows a few correlations (correlation is different than causation): Supination/Pronation Ratio, Percentage Split Finger Changeups, Fastball Velocity, and Fastball Velocity Drops.
Diamondbacks. Games thru 23 July 2025. Data from Baseball Savant.