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Tyler Glasnow’s 97 mph cutting fastball is unusual and absurd

Glasnow made some major adjustments before the start of the 2018 season, and the Rays are reaping all of the benefits

Tampa Bay Rays v Chicago White Sox Photo by Jonathan Daniel/Getty Images

If there is one thing where Rays pitchers most definitely lead the majors (besides team ERA and team FIP), it’s viral pitching GIFs. The latest of these came from starter Tyler Glasnow during Wednesday’s game against the Chicago White Sox:

97 MPH cut action is not normal!

What’s interesting about this pitch is that Tyler Glasnow has never actually thrown a true cutter, yet this pitch had over five inches of cut action, and his fastball seemed to have that major cutting action all afternoon.

Was this by accident, or did Glasnow develop a new pitch overnight? To answer this question, we need to take a trip to 2017.

That year, the Pirates would give Glasnow his first shot at a full time major league role, when he made the team out of camp as the Bucs’ fifth starter. But things wouldn’t go well, as the team’s top pitching prospect became extremely hittable, pitching to a 7.69 ERA and a 6.30 FIP. To boot, his K% was a mere 18.4%. This performance justifiably earned him a demotion.

He returned to form during his time back in AAA, but after his second major league sample, it seemed like his skills weren’t translating at the game’s highest level. That offseason, Glasnow would train at the renowned Driveline baseball facility in Kent, Washington.

After a winter of training with the leading experts in such New Age pitching concepts as spin rate, pitch design, and pitch tunneling, the returns for Glasnow were immediate:

Tyler Glasnow 2017 vs. 2018

Year fastball spin spin percentile pitch speed whiff% K% K% percentile
Year fastball spin spin percentile pitch speed whiff% K% K% percentile
2017 2236 42nd 94.6 15.5 18.4 25th
2018 2365 79th 96.5 23.3 29.1 85th

Though he was able to ascend through the minors with his raw ability and tools, unlocking his spin rate potential was the missing link he needed to find major league success.

Now, let’s talk about that cutting action.

One of the other adjustments he made that offseason has to do with his arm angle upon pitch release:

This not only bore a strong correlation to his increased spin rate of his fourseam fastball, it also changed the horizontal movement of the pitch.

What was a normal fastball with armside run (for a righty that’s negative horizontal movement) became a more unusual fastball with no horizontal spin deflection, on average:

Averages can be deceiving, though.

Look at Glasnow’s results from 2018 on the per-pitch level:

Tyler Glasnow, 2018

The red clump is a group of fastballs centered on the zero marker, but we can see the movement on this pitch is more fluid, with points on either side showing many fastballs with real armside run, and many fastballs with gloveside cut. The average of the pitch is 0 horizontal movement, but sometimes there’s noticeable break in either direction.

Compare Glasnow to fellow 2018 Rays righty, Nathan Eovaldi, who throws a traditional fastball, as well as a traditional cutter. In Eovaldi’s case, it’s clearly two separate pitches, rather than one pitch with a meaningfully different range of movmement.

Nathan Eovaldi, 2018

Eovaldi’s fastball (the red clump) and his cutter (the yellow clump) are distinct from each other. They’re also separated, on average, by five miles per hour. Because the movement range for Glasnow from armside run to gloveside cut is continuous, accomplished by minor variations in a single pitch type, he gets high-90s velocity no matter which direction the ball is moving.

If we look further into how he grips the pitch, we can see how he gets that variability without having to throw a true cutter:

Tampa Bay Rays v Chicago White Sox Photo by Jonathan Daniel/Getty Images

While most pitchers throw the fastball with their index and middle fingers together, Glasnow (who we can safely assume has larger hands than the average pitcher) is afforded the luxury of spreading his fingers, with his thumb positioned on the middle finger side of the baseball.

We can continue to compare this to Eovaldi, whose fingers are much closer together:

Boston Red Sox v New York Yankees Photo by Jim McIsaac/Getty Images

For Glasnow, the split grip allows him to tilt the axis of the ball simply by adding minimal pressure with the middle finger. In contrast, Eovaldi needs needs to alter his grip in order to get similar action, and along with that comes the sacrifice in velocity.

The result for Glasnow is being able to go from this, a more traditional rising fastball:

To this, the cutting fastball, without sacrificing velocity:


Could this be random variance? Possibly. If not, it’s going to be a rough go for anyone who faces him this year. Either way, we could be witnessing something special.