Heading into the 2020-21 offseason, Tyler Glasnow was the Rays No. 3 starting pitcher in the depth chart. But after declining Cy Young contender Charlie Morton’s option and trading Cy Young winner Blake Snell to San Diego, Glasnow is now the team’s opening day starter.
This would have seemed like a logical progression after his stellar 2019 campaign when he pitched to a 1.78 ERA/2.26 FIP in 60.2 innings of work, but his ‘20 season left a little more to be desired, pitching to a 4.08 ERA/3.66 FIP—still good, but was it ace good?
Although Glasnow’s run prevention took a significant hit from ‘19 to ’20 (re: higher ERA), he was better in some key areas.
For one, his strikeout rate and whiff rates both improved from levels that were already elite. In ‘19, Glasnow ranked in the 91st percentile in K% and 71st percentile in Whiff%. In ‘20, those numbers shot up to the 97th and 83rd percentiles, respectively.
All told, while Glasnow missed more bats, there were a few areas in which he did run into some trouble.
You could have expected better
Fielding Independent Pitching, or FIP, is a metric that strips a pitchers performance down to the factors they have more control over, their ability to get strikeouts, limit walks, and limit home runs (also known as the “three true outcomes”). In ‘19, Glasnow was not only exceptional at preventing runs, he was also great at influencing these more controllable outcomes. For pitchers who threw a minimum of 60 innings that year, Glasnow’s 2.26 FIP was 4th best in baseball.
But the main flaw with FIP is that while pitchers have limited control over whether balls in play become hits, they similarly have limited control over whether fly balls become home runs.
Expected Fielding Independent Pitching, or xFIP, controls for this flyball variance by normalizing a pitcher’s home run to fly ball rate to the league average. Both FIP and xFIP are good ERA predictors, and both read like ERA. Put another way, if it’s a good ERA, then it’s a good FIP/xFIP.
Glasnow’s aforementioned 2.26 FIP in ‘19 was heavily influenced by an absurdly low 8.5% HR/FB%; almost half the league average that year. In contrast, Glasnow’s 3.66 FIP was buoyed by 23.4% HR/FB%; or roughly 50% above the league average.
Looking at xFIP for the two years in question, we can view Glasnow’s ‘20 performance from a different lens, as well as paint a clearer picture for his 2021 outlook:
Tyler Glasnow Peripherals
Taking the randomness of home runs and fly balls into account, Glasnow’s performance actually improved, thanks to his increased ability to miss bats. This is the guiding principle of xFIP, and is why it is a more useful ERA predictor than is ERA itself. Of course, projecting pitchers isn’t quite that simple.
Tunnel of glove
In addition to Glasnow’s ability to influence three true outcomes, he also was very good at limiting hard contact in ‘19.
In metrics such as Exit Velocity, HardHit%, Barrel% and xwOBA, he ranked in the 79th, 83rd, 74th and 99th percentiles (where higher percentages mean better performance). Compare that to ‘20 when he ranked in the 16th, 20th, 28th and 79th percentiles in the same categories. This could be natural regression, or it could be that hitters adjusted. Even though hitters still had trouble making contact, when the did connect, they did more damage.
Glasnow’s effectiveness is tied to his ability to deceive hitters by tunneling his pitches, so long as his glove position isn’t tipping hitters off to what’s coming. Since he has primarily been a two pitch pitcher, he does this by using his fastball at the top of the zone, while using his curveball at the bottom of the zone.
To see this in action, consider the following GIF from an at-bat against Mike Tauchman, first with the pitches side by side, then overlaid.
In ‘19, both of Glasnow’s pitches rated as elite. His high speed four-seam fastball, which sometimes featured some unusual cutting action, netted an average EV of 88.4 MPH and and xwOBA against of .293—both of which being well below average. And his curveball was deadly, generating nearly 44% of whiffs per swing. Even when hitters made contact, it was only to the tune of an 84.2 MPH EV and .116 xwOBA. Hitters either didn’t make contact with Glasnow’s curveball, or they wish they didn’t.
While the curveball was even better by some metrics than it was in the previous year, the fastball took a step back, generating a 91.2 EV and .343 xwOBA. Per Texas Leaguers, Glasnow added an inch of rise and 130 RPMs of spin to his fastball in ‘20, but seemed to have lost at least some of the glove side movement that that made the pitch so unique in the prior year.
Although it is reasonable to expect four-seamers to get hit harder than secondary pitches, this is pretty big difference from one year to the next. It’s hard to say whether the change in movement made the pitch easier to hit, but one can imagine it’s a bit tougher to square up a pitch that has a higher variability of movement than one that doesn’t.
In addition to Glasnow’s fastball getting hit harder in ‘20, what is also interesting is where it was hit harder. Using Baseball Savant’s illustrator tool, we can look up exit velocity heat maps by pitch. Here are those maps for his fastball from ‘19 (left) and ‘20 (right)
Hitters did more damage on fastballs up in the zone against Glasnow in ‘20. Since he primarily lives there in order for the curveball to play well off of it, hitters seemed to have adjusted. Even with some improved movement, as represented in metrics such as spin rate and rise, it’s possible that hitters were hunting the fastball up in order to take away one of Glasnow’s weapons.
So how will Glasnow adjust back?
Glasnow’s full arsenal
At the start of this spring Glasnow revealed that he was working in a slider/cutter hybrid in hopes of having a third offering to further befuddle major league hitters. In most recent interviews he’s simply called it a slider, so we will as well.
So far, he has had one outing where his pitches were tracked by Statcast, and the results on the slider were good. Once again using Baseball Savant’s illustrator tool, here is how the new pitch compares to his fastball and curveball:
The shape of the pitch shows some pretty solid separation in movement from his fastball and curveball, although the velocity did not keep its separation from the curveball as he continued to try the new stuff.
In the small sample of this outing, of the 25 sliders he threw, he averaged roughly 87 MPH compared to 84 MPH on his curveball. In practice, this opens a lot of new ways that Glasnow can get hitters out.
The shorter vertical action means that he can pitch effectively with the fastball in more areas of the zone, making it harder for hitters to hunt a particular pitch in a particular spot.
But even with the good results so far, Glasnow admits the pitch still needs some work, specifically saying that he would like it to have a little more velocity and more horizontal movement.
Instead of making his next pitching appearance in front of limited fans, Glasnow returned to the lab to continue working on the new pitch, and here is what he had to say about it during a pregame interview on March 22:
I shifted the grip and I am super comfortable with it now. Velo was 85-89 and it was too slow, too much like my curveball. I had to get it more horizontal and it was 88-92 today so that’s perfect.
This is a promising development, as creating more velocity separation from the curveball should help Glasnow fool hitters’ timing even more. If Glasnow is able to make the necessary changes, he could have yet another elite weapon in his pitch arsenal.
Conclusion: Team leader ready to be the star
There is quite a bit to unpack here, so here is a more concise summation of what I have presented:
- Tyler Glasnow was one of the best pitchers in all of baseball on a rate basis in ‘19. However, his run prevention was heavily influenced by a HR/FB% that was about half the league average.
- In ‘20, even though Glasnow took a step forward in some respects, such as his ability to miss bats, his run prevention took a step back, thanks in part to an overcorrection in his HR/FB%, which ballooned to 23.4%.
- By a metric called Expected Fielding Independent Pitching, which predicts ERA by controlling for fluctuations in HR/FB%, Glasnow performed better in ‘20.
- Glasnow’s fastball got hit pretty hard in ‘20 after rating as an elite pitch in ‘19. In particular, hitters did much more damage on the pitch when it was thrown up in the zone, meaning that hitters adjusted to his arsenal.
- Because of this, Glasnow has introduced a third pitch this Spring as a means to increase his pitch deception and find a new way to generate swings and misses.
Steamer and ZiPS of FanGraphs both believe that Glasnow will be one of the better starting pitchers in baseball, and that is without factoring in the added effectiveness a new pitch may bring. Both systems out put a projection north of 3.0 fWAR, making him anywhere from a top 15-20 pitcher on a rate basis.
Glasnow’s has shown ability to make positive adjustments throughout his career. He has the self-awareness to know when he needs to improve, and a hunger to take the next step. This bodes well for him and the team that is depending on him.
Some say that the ‘21 season will be a transition year for the Rays starting rotation. That is true in at least one sense—that Glasnow will transition into the ace of the pitching staff.
Long a team leader in the clubhouse, among the pitchers, and as the MLB Player’s Association union rep, Tyler Glasnow is finally on the cusp of becoming the pitcher his potential has always promised he could be.