After watching Tyler Glasnow crush Triple-A opponents to the tune of 133 strikeouts and a sub-2.00 ERA over 110 innings in 2016, it was disappointing to see him unable to translate his success to the majors in a year the team so desperately needed to bolster its rotation.

Like a few other Pirates last season, Glasnow was adequate the first trip through the order but struggled to keep hitters off balance the second and third times he faced them, going from a palatable 3.95 FIP to well north of six. Several issues contributed to the difficulties, but the root of the problem was the lack of a true third offering. Consequently, Tyler Glasnow’s fate this spring is ultimately dependent not on out-dueling the competition, but on demonstrating he has the ability to utilize a third pitch.

Glasnow’s 2016 “third pitch”

Glasnow has long possessed a changeup in addition to his plus fastball and curveball, but it’s hardly worth designating it a third pitch given the complete lack of confidence in using it. In fact, he only tossed seven to 11 changeups in the majors last season, and that discrepancy in number is more a reflection how poor the changeup was rather than a flaw in the system.

After all, an effective changeup needs to both convince a hitter that a fastball is coming, and as the name of the pitch indicates, show separation in velocity and/or movement from the primary pitch. Let’s examine to the degree to which Glasnow’s changeup failed to do those things.

Velocity

In 2016, Marco Estrada of the Toronto Blue Jays had one of the ten lowest average fastball velocities among qualified starting pitchers. He occasionally came close to touching an electric 91 MPH but was typically around 88 MPH. With those numbers, one wouldn’t expect Estrada to possess one of the top changeups in baseball. He actually did, though, largely because a strong changeup is not about having serious heat (though that doesn’t hurt).

Instead, an effective changeup is more the result of a healthy velocity differential between the changeup and fastball, and that is exactly where Estrada thrived. His average velocity differential between his fastball and his changeup was more than 10 MPH, good for top five in the league. There’s more to both his and others’ changeups than simply a velocity change, but we’ll get back to that in a second.

In contrast, Tyler Glasnow held quite the dismal variation as is depicted below:

The average variation between the two pitches was a meager 4.6 MPH, which ranks exceedingly low the on the differential scale for starting pitchers.

To be fair, Glasnow throws significantly harder than Estrada, so it was worth comparing his numbers to a few guys who can throw in the mid to upper 90’s. Exactly 16 qualified starting pitchers averaged a harder fastball velocity than Glasnow, and of those 16, the only one who threw a harder changeup was Noah Syndergaard. Thor rightfully should considering he occasionally hits triple digits and regularly throws over 97 MPH, but it’s not promising that Glasnow threw harder changeups than all the rest. It also doesn’t bode well for Glasnow that the only pitcher in the sample remotely close in average differential was Jake Arrieta, with a five-MPH differential.

Movement

Despite the similarity in velocity differential between Arrieta and Glasnow, their movement charts reveal a very different trend in movement.

Even if Arrieta does not have ideal velocity variation between his four seam and his changeup, there’s distinguishable movement both horizontally and vertically, a characteristic that Glasnow has lacked. Glasnow’s spray charts suggest his changeup is essentially just a slower version of his fastball, which explains why there’s a discrepancy in the number of changeups.

Let’s now explore how Glasnow stands up to the rest of the league’s starters. Our first table below is taken from Eno Sarris of Fangraphs, who created it to depict the average horizontal (xMOV) and vertical movement (zMOV) of both fastballs and changeups during the 2015 season. A negative horizontal number for a right-handed pitcher means the pitch is running in on a right-handed batter, while a positive number means the pitch is moving away. Similarly, a negative vertical or simply a smaller number means there’s more drop.

Since a changeup has less backspin than a four seam fastball, it’s going to both drop and move towards the batter more over the longer flight time to the plate.

The grip and movement of Glasnow’s changeup may technically be enough to categorize it as a different pitch from the four-seamer, but the numbers underline the notion that it’s really just a slow fastball with slightly more drop. This apparently wasn’t lost on Glasnow, who said of his changeup, “It was 92 and didn’t move at all … so if I threw it, it would be a bad fastball.”

The incredibly small sample size doesn’t mean this was all Glasnow was capable of with his changeup, but it does show how useless it was to him and hint why he opted not to use it more than a handful of times.

Compensating for lack of a third offering

Operating on two pitches in the minors can work if you possess the wicked stuff Glasnow does, but with less in the arsenal, the strategy becomes entirely dependent on varying the speed and location, which requires a great deal of control that Glasnow is still learning to harness. The combination of poor control and being forced to pitch with that strategy resulted in his clearly above-average fastball being hammered by opposing batters, who produced a 144 wRC+ against it.

Four-seam Fastball

To put things in perspective, I juxtaposed Glasnow’s fastball “Plate Discipline” statistics next to a few of the most valuable fastballs in the game among starters in 2016. These statistics typically provide insight into a pitcher’s control and ability to keep hitters off balance.

Glasnow threw 275 four-seam fastballs last season with just over 48 percent of them crossing in the strike zone, which is a far cry from the percentage of the top two guys. Meanwhile, he clearly exhibited swing-and-miss talent, keeping pace with the top two while simultaneously limiting contact.

Overall, hitters were less likely to swing at his pitches, but it’s difficult to ascertain how much of their reluctance is due to his inability to locate the fastball. But at 20.6 percent, his O-Swing% (the swing percent on pitches outside of the zone) leads one to believe a high number of fastballs tossed that no one was chasing rendered batters more hesitant to swing because they just didn’t have confidence that it was going to be a hittable pitch. It may sound like a boon, but it is hard to take advantage of an excellent swing strike percent if the batters never chase the ball out of the zone, especially when the majority of his fastballs landed there.

It isn’t displayed in the table, but when he did locate the fastball and they managed to make contact, they produced an exorbitantly high line drive rate, 41 percent, that’s probably a combination of luck and predictability that should regress towards normal moving forward.

In terms of velocity and movement, Glasnow’s fastball was not oversold in the slightest. He typically maintains velocity as the game progresses with the ability to dial it up when necessary. The one knock on his fastball here is the same as it was when he was coming through the minors—that his tall frame makes it difficult to repeat his delivery, and at times, he’d cut the delivery off slightly early, resulting in less movement. On the bright side, he’s spoken to reporters about cleaning up his delivery this offseason to rectify the problem, so it could be interesting to gauge this spring.

Curveball

Glasnow’s curveball has exactly what you want; strong movement that bites down as drastically as anyone’s (-8.1 zMOV) and solid velocity separation (14.3 MPH) from the fastball. Clint Hurdle preached the latter at the Winter Meetings when he answered the following in response to a question on the difficulty of hitting a good curveball:

It all depends on the fastball velocity that enhances the whole thing. Because when you can separate the velocities, when you can get a breaking ball and curveball velocity 15 to 20 miles apart that’s when it’s really challenging. If you’re throwing 88 miles an hour and your curveball is 77 miles an hour, there is not enough separation. So it’s easier to time, to anticipate and to put the barrel on it. So I still think it’s a lot about separation. You’ve got to have fastball command, fastball location to set up the other pitch.

Perhaps Glasnow will be encouraged to add slightly more separation, but he’s already at a respectable differential.

While the zone percent for a curveball is bound to be lower since you’re relying on a heavy break, Glasnow’s is also indicative of well-known control issues. The elevated contact rates both in and out of the strike zone in conjunction with low swing rates suggest again that hitters were patient or hesitant because he was throwing a lot of curveballs that were clearly balls. And if you peruse Glasnow’s pitch tunneling statistics for his pitch pairs, you’ll see that the trajectory of his curve easily tipped off batters what was coming a fair amount of the time.

On the bright side, the solid swinging strike percent coupled with the stellar .205/.300/.384 slash line off his curve means his curveball was extremely difficult to hit well even if it was predictable at times.

An improved repertoire

There are a lot of things about Glasnow’s debut that are still murky because of the absence of a true third pitch, but that is supposedly going to change this year. After a busy offseason of work, Glasnow is set to debut a four-pitch repertoire this spring. He’s added both a two seamer and altered the grip on his changeup, and all reports this spring have him utilizing them frequently in an effort to find a level of comfort.

Without a doubt, this is the sort of adjustment Glasnow needs to make to go from highly-touted prospect to an effective major league pitcher (or hopefully an ace). Perhaps he’ll show a good feel for mixing pitches and harnessing his new four-pitch arsenal right out of the gate, but it would behoove the organization to ensure he has confidence using at least one of the new pitches, even if that involves some seasoning in the minors.