Rotation, Bullpen, or St. Paul: Analytically Breaking Down Zebby Matthews’s Arsenal

[Lucas Seehafer PT]

Perhaps no other Twin in recent memory saw their prospect stock rise more rapidly than Zebby Matthews. Selected with the 234th pick in the 2022 draft out of Western Carolina and signed for a paltry $125,000, Matthews grew from an afterthought to a top prospect at virtually the speed of light, debuting by mid-August 2024.

Unfortunately, Matthews’s once-bright flame has dimmed in the eyes of some, due to inconsistent performance across 117 major-league innings. His rise was fueled by an uncanny ability to live in the zone, missing bats and not giving up any walks, while drastically improving his fastball velocity. In the majors, his walk rates have nearly tripled from approximately 2.0% in the minors to 6.6%, while his strikeout rates have dropped by roughly eight percentage points.

These decrements in performance, albeit in a relatively small sample, have begun to beg the question: Is Zebby Matthews’s future in the starting rotation or the bullpen?

Read Previous Entries:

• David Festa's Arsenal

Zebby Matthews’s Stuff & Pitch Arsenal

On paper, Matthews boasts a prototypical 2026 starting pitcher repertoire. He primarily relies on his four-seamer and slider, dispatching them against lefties (293 and 140, respectively, in 2025) and righties (263 and 199) at an equal clip. Matthews employs his cutter slightly more often against left-handed hitters (103 vs 73), though the sample size for each is quite small, and virtually only throws his changeup against lefties (104 vs. 39). Sprinkle in the occasional curve and sinker to keep hitters on their toes, and Matthews arsenal is sufficient for a starting pitcher… in theory.

In practice, at least at the MLB-level to date, Matthews really only has one pitch that has performed well: his gyro slider. As shown in the movement profile graph and implied in the slider heat map above, Matthews’s slider features significantly more drop (vertical break) than it does sweep (horizontal break). This is due to the pitch featuring more gyroscopic (think football spiral) spin than side spin. Gyroscopic spin does not influence pitch movement, meaning that the majority of the ball’s movement is simply due to the pull of gravity as it flies through the air.

Across 525 major league offerings, opposing hitters have managed a meager .568 OPS against Matthews’s slider, per FanGraphs, driven by a high-30% whiff rate in combination with a 42% ground ball rate. In essence, when Matthews’s throws his slider there’s high chance that the batter is either going to miss it entirely or pound it into the ground.

The rest of Matthews’s arsenal has been varying degrees of lackluster, even this four-seam fastball, whose crazy velocity creep helped him rapidly rise through the minors. Pitchers can overpower minor league hitting with pure velocity, something Matthews and his mid-90s fastball accomplished. However, the same can’t be said for major league hitting. Generally speaking, if a fastball is going to be a pitcher’s best offering in the majors, it not only needs to possess high velocity readings but also have a movement profile that makes hitting it squarely extremely difficult. MLB hitters can hit straight gas; hitting moving or deceptive gas is much more difficult.

When analyzing the movement profile, or shape, of a fastball, there are two metrics worth considering: induced vertical break and horizontal break. Induced vertical break measures how much the ball drops solely due to its spin, taking gravity out of the equation. If a fastball has a high degree of spin, it will, more often than not, register a higher induced vertical break, meaning it doesn’t drop. This will produce an illusion in the hitter’s brain, making it seem as though the ball is rising. Horizontal break measures how much the ball moves, well, horizontally; if it moves towards the glove side of the pitcher, we say it has ‘cut’, and if it moves towards the hand side, we say it has ‘run’.

Year	Pitch Type	#	# RHB	# LHB	%	MPH	PA	AB	H	1B	2B	3B	HR	SO	BBE	BA	XBA	SLG	XSLG	WOBA	XWOBA	EV	LA	Spin	Ext.	Whiff%	PutAway%
2025	Four Seamer	556	263	293	41.1	96.2	123	112	40	25	8	0	7	30	85	.357	.303	.616	.571	.422	.394	92.7	23	2331	6.6	22.4	19.4
2025	Slider	339	199	140	25.1	88.2	113	107	16	11	2	0	3	50	58	.150	.184	.252	.326	.193	.237	87.5	10	2419	6.4	38.5	24.3
2025	Cutter	176	73	103	13.0	91.7	54	42	14	12	1	0	1	3	40	.333	.318	.429	.482	.405	.414	88.7	15	2494	6.5	24.2	8.6
2025	Changeup	143	39	104	10.6	87.5	32	31	11	7	3	0	1	1	31	.355	.317	.548	.426	.374	.346	86.3	6	1499	6.4	26.3	5.3
2025	Curveball	79	38	41	5.8	82.9	14	14	5	4	1	0	0	2	12	.357	.304	.429	.487	.342	.338	88.9	38	2435	6.3	34.5	10.5
2025	Sinker	60	58	2	4.4	95.8	18	17	8	8	0	0	0	2	16	.471	.264	.471	.320	.415	.255	77.2	6	2317	6.6	7.7	50.0
2024	Four Seamer	307	115	192	42.8	94.9	66	59	17	7	5	0	5	17	42	.288	.262	.627	.592	.417	.394	94.3	19	2230	6.5	17.8	21.3
2024	Slider	186	92	94	25.9	87.2	57	52	16	12	2	0	2	20	32	.308	.251	.462	.400	.363	.318	90.2	11	2349	6.4	37.6	23.5
2024	Cutter	116	62	54	16.2	90.9	30	29	10	7	0	0	3	2	27	.345	.295	.655	.674	.434	.418	87.3	17	2403	6.4	18.2	18.2
2024	Changeup	57	2	55	7.9	85.8	9	9	2	1	1	0	0	0	9	.222	.348	.333	.512	.237	.378	86.6	-5	1550	6.4	31.3	0.0
2024	Curveball	51	9	42	7.1	81.7	15	15	6	4	1	0	1	4	11	.400	.327	.667	.558	.455	.377	87.9	16	2369	6.3	17.4	14.8

Generally, there is a trade-off between a fastball’s induced vertical break and horizontal break; more in one generally leads to less of another. This is where Matthews’s fastballs—both his four-seam and sinker—struggle. The induced vertical break of his four-seamer is 16.6 inches, and his horizontal break is 9.0 inches of run; for his sinker, it is 13.1 inches and 15.2 inches, respectively. These are what are known in the industry as “dead zone” fastballs. Essentially, to the batter’s eye, they appear straight, not having enough induced vertical break to produce the rising illusion and not enough horizontal break to be difficult to square up.

Since Matthews’s made his debut, opponents have produced a .944 OPS (839 pitches) against his four-seamer and a 1.368 OPS (82 pitches) against his sinker. His cutter (.955; 294), changeup (.817; 200), and curve (.931; 130) haven’t fared much better.

However, there are some intriguing data points embedded within Matthews’s splits statistics. Namely, they suggest that he is much better against righties than lefties to the tune of .230 points of OPS (.944 OPS against 278 lefties and .714 OPS against 253 righties) and 4.0% K-BB% (20.2% vs. 16.2%). Which informs…

What Should Zebby Matthews’s Role Be In 2026?

It’s extremely difficult to be an MLB-caliber starting pitcher with only one good pitch. Luckily, carving out a productive career out of the bullpen is relatively achievable. Matthews’s career to date is not all that dissimilar to that of Glen Perkins, Tyler Duffey, and, more recently, Griffin Jax. These were all starting pitchers who experienced great success in the minors before struggling mightily once they reached the majors because their middling repertoires were exposed. However, a shift to the bullpen and increased emphasis on their best pitches transformed them into, at times, devastating backend relievers.

For Matthews to project as a starting pitcher moving forward, he likely needs to add at least one more above-average pitch—perhaps a sweeper or kick-change to complement his gyro slider?—and/or improve the shape of his fastball. Neither is a particularly easy task, though adding a new pitch is significantly more trainable than adding isolated pitch spin/induced vertical break. The Twins have far more metrics available to them, including whether Matthews is more of a natural pronator or supinator, which would influence which pitches would be easier to add, as well as linear and rotational force-velocity data, which would indicate if there is any additional athletic performance meat being left on the bone.

The Twins may continue to employ Matthews as a starter, but, as things stand right now, his profile is much more suitable for a bullpen role. 

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[JD-TWINS]

The stats are a pretty big slap in the face, IMO, for those who insist he’s a real talent and needs to remain a starter for sure. I don’t have a crystal ball to gauge how he may or may not improve. He’s going to be 26 in 2026 ….. he was a low round draft pick and a great story in ‘24’s meteoric rise. That said:

It seems he should eliminate his Sinker - Cutter - Curveball, based on the metrics shown above on OPS and focus on 3 pitches to use at a higher effectiveness rate from the back end of the PEN.

With 1 inning stints he can throw his 4 seamer 96-98, which with proper location, will be effective. The slider needs to be the pitch he throws 50% of the time. The change-up as a waste pitch in & off the plate to righties about twice a week for show and then as a more effective offering to lefties he’ll face. The focus with 3 pitches would hopefully help him refine location skills and help him relax with far fewer pitches to master…………maybe he keeps the curve as a second “show pitch” and throws it 4-5% of the time. Theorizing the change-up is 15% with the Slider at 50% and Fastball at 30+%.

I think he’s an 8th-9th inning guy as he gains experience and gets comfortable in a new role.

6 pitches with only one of real positive effectiveness doesn’t get me excited for him to be a rotation guy!

[Mahoning]

It's a sophisticated analysis that could also be expressed more simply: If you can't go four innings without getting lit up, off to the bullpen you go.

[terrydactyls]

Hitting straight gas or deceptive gas is impossible.  Regardless of whether the gas is nitrogen, oxygen, noble, or deceptive, gas by definition is a non-solid and you can't hit something with a bat that isn't solid.

[Lucas Seehafer PT]

Just now, terrydactyls said:

Hitting straight gas or deceptive gas is impossible.  Regardless of whether the gas is nitrogen, oxygen, noble, or deceptive, gas by definition is a non-solid and you can't hit something with a bat that isn't solid.

😑

[DJL44]

From what I saw, Zebby was great at hitting the corners in 2024 but lacked velocity which meant everything got fouled off. He added velocity in 2025 but started missing the corners, leaving the ball over the plate while also increasing his walks. If he can combine the added velocity with the excellent location he showed earlier he can make it even without adding spin.

[LA Vikes Fan]

Interesting analysis. In a way, this reminds me of the analysis regarding David Festa. Both Matthews and Festa have a very high-quality non-fastball option. Both, however, suffer as a starter because the fast ball just isn’t quite good enough to go through a major league banning order more than once. Both also have other secondary options, which are not so great but could be improved.
 

The question then is to you move one or both to the bullpen and play to their strength by emphasizing their strong secondary pitch and gain a ticker two on the fastball by throwing it in shorter stance, or do you try to improve that fastball by either improving it’s cut or run or improving It’s control such that these guys can hit corners regularly? I do think the answer is different from the two primarily because of physical health. Festa‘s got a shoulder issue that is going to limit his innings in 2026. I would put him in the bullpen and then decide after 2026 whether to leave him there. I would leave Matthews as a starter, start him in Saint Paul to begin the season, and see if he can either improve the fastball or one of his other secondary offerings enough to be effective at the major league level.

[TJSweens]

My guess is that he is going through one of the off-season pitching academies the Twins have for their prospects. He's probably working on modified grips and trying new pitches. 

Matthews is a good candidate to start the year in the pen. He has nothing more to prove in AAA. The usual uptick in velo that accompanies a move to the pen should make his fastball more effective. The short stints should also make it easier to break in a new pitch or a modified existing pitch. Matthews also has enough innings under his belt to make it easy to stretch him back out if they want another look at him as a starter. 

[CRF]

Bullpen.

[JD-TWINS]

19 minutes ago, DJL44 said:

From what I saw, Zebby was great at hitting the corners in 2024 but lacked velocity which meant everything got fouled off. He added velocity in 2025 but started missing the corners, leaving the ball over the plate while also increasing his walks. If he can combine the added velocity with the excellent location he showed earlier he can make it even without adding spin.

His ERA in ‘24 was 6.69 so he wasn’t getting the ball past too many guys on the corners………..his “control” in the minors was fantastic if the BAR is just not walking guys …… he overpowered MiLB hitters. His command in the zone has been lacking at the MLB level. Probably wasn’t any better in MiLB.

The ERA went down 1.1 runs in ‘25 to, a not MLB sustainable, 5.56.

At 26, my opinion is that he is what he is (he obviously can evolve & improve) & he’s trying to master SIX pitches which is a very lofty pursuit! Trim to 3-4 pitches and “contribute effectively” from the PEN v. just filling a void for innings in the rotation as has been the case over the past 2 years.

Duran - Jax - Stewart - Varland all have better stuff and were squarely in the Twin’s PEN - no disgrace in doing what you’re good at or being allowed to succeed in a new role.

[Linus]

What this, combined with the other Twins pitching scouting reports tells me is that the late round college pitcher who we can add velocity to premise isn’t the market inefficiency that the Twins were banking on. Perhaps the pitchers taken in early rounds are better after all. 

[Lucas Seehafer PT]

3 minutes ago, Linus said:

What this, combined with the other Twins pitching scouting reports tells me is that the late round college pitcher who we can add velocity to premise isn’t the market inefficiency that the Twins were banking on. Perhaps the pitchers taken in early rounds are better after all. 

I don’t think that’s necessarily true. Especially if the Zebbys, Festas, etc. develop into high-end relievers. Turning an eighth-round pick (who rarely even make the majors) into a 100 mph solid bullpen arm is much more of a market inefficiency that turning a first or second-round pick into the same.

[miller761]

Velo and spin are nothing without command and control.

[LambchoP]

Adding Festa and Zebby to the pen could really help out our weak relief corps. I'd still give him another few months to see if he can make it as a starter. Twins need to decide between Zebby, Bradley and Abel on who will start and who gets moved to relief. Should be an interesting spring training to see what they do with the pitching staff.

[Linus]

29 minutes ago, Lucas Seehafer PT said:

I don’t think that’s necessarily true. Especially if the Zebbys, Festas, etc. develop into high-end relievers. Turning an eighth-round pick (who rarely even make the majors) into a 100 mph solid bullpen arm is much more of a market inefficiency that turning a first or second-round pick into the same.

I’m assuming the goal is to develop starters not relievers. 

[OregonTwinsFan]

I would keep him as a starter. He has had some great games and just needs to be more consistent...which comes with experience. I could see him having a break out year.

[Danchat]

Zebby has had an easier time going later into starts than Festa and SWR so I assumed that meant he might be closer to a breakthrough, but after seeing the data that may be a faulty premise. I wouldn't move him to the pen yet, but it should be under consideration.

[Galen]

Let the man pitch

[HerbieFan]

At 26, I think his path forward is clear given where and why he's struggled.  It's the 'pen for me.

[jmlease1]

It is a really interesting question with Matthews. He's got the velocity to be effective with his fastball, but doesn't have the shape for hitters to not catch up to it once they get the timing down, at least not right now. Is that something that can be fixed for him with changes to his grip, arm slot, etc or is that something that simply isn't going to be very fixable?

If it's something that offseason adjustments can address, you look at leaving him in the rotation; the changeup could improve with a better fastball to play off of or simply from working more with the pitch, and the slider is definitely a weapon for him. That could easily be a workable mix and he could keep working on a cutter or a sinker as an additional offering.

If changing the shape of his fastball is simply not a reasonable expectation, then I guess he'll be finding better success in the bullpen, when no one gets that second look at his fastball (and maybe it ticks up another couple of mph) and he can throw 50% sliders and drive people crazy while he works on the change.

I'll admit, I don't know whether or not it's realistic for him to adjust the fastball to give it the kind of movement/deception required to be an effective starter. It's certainly true that you can't overwhelm most MLB hitters with straight gas.

[rdehring]

Another great post and fantastic comments.

Sounds like there is a real chance that both Zebby and Festa are better suited for the pen.  Perhaps the Twins are also of this opinion, which may be why they haven't been overly concerned with signing a bunch of middle of the pack relievers for $xM each.  They may feel that both of these guys will be at least that good.

[JD-TWINS]

2 hours ago, Linus said:

I’m assuming the goal is to develop starters not relievers. 

I get it, but a Team (staff) needs 5 starters with 2-3 alternatives in a typical rotation for a season…….while they need 8 relievers and 3-4 alternatives in the PEN for a typical season. Plenty of room for guys not in the first 3 rounds to be developed into real assets!

[JD-TWINS]

Is Matthews, with his pedigree and level of success over ‘24 & ‘25 at MLB, a better bet than Taj Bradley?

How does he stack up with Abel’s stuff and probable capabilities ……& age?

I get he’s a sentimental favorite but ESSENTIALLY EVERYONE here thought Varland should continue to get endless shots at being a starter as well. It’s time for Zebby to move to the PEN & trim his 6 pitch offering to 3-4 that work.

[Linus]

1 hour ago, JD-TWINS said:

I get it, but a Team (staff) needs 5 starters with 2-3 alternatives in a typical rotation for a season…….while they need 8 relievers and 3-4 alternatives in the PEN for a typical season. Plenty of room for guys not in the first 3 rounds to be developed into real assets!

Thats kind of the point - they purposely avoided using higher draft picks on pitchers for the first half or more of Falveys tenure because they deemed it too risky and that they had the secret sauce on these later round college guys. Some of them will be good relievers but that particular strategy hasn’t worked to develop starters as they originally hoped it would. I also understand they have acquired good starters via trade and they get a hot tip for that but in that you have to give to get. 

[Paul Walerius]

If I have said it once, I have said it a million times, Zebby has the mentality and stuff to be a very good closer.  Or at a minimum a very good setup pitcher.  

 

 

[Blyleven2011]

4 hours ago, Paul Walerius said:

If I have said it once, I have said it a million times, Zebby has the mentality and stuff to be a very good closer.  Or at a minimum a very good setup pitcher.  

 

 

I also agree he could be a good late inning bullpen pitcher , set up man first , Bradley might be closer material , he's bomb out as a starter so is destined for the pen ...

I think matthews get Another Crack to start the season as a 4th or 5th starter

[PuckettProtector]

I've said from the get go his stuff doesn't play as a starter. He needs to be in the bullpen. 

[PuckettProtector]

I've said from the get go his stuff doesn't play as a starter. He needs to be in the bullpen. 

[thelanges5]

Lopez, Ryan, and Bradley will be at the WBC so there will be plenty of innings available for Zebby and Festa in ST. Keep them stretched out for now, no need to make the decision until later in camp.

[stringer bell]

Lack of walks doesn't equal command. Zebby got behind too many hitters and paid the price over and over. That 98 mph heater is a lot better pitch on 0-2 than it is on 3-1.

I think Matthews is one of the 12 best arms and should start the season with the Twins. I also don't think the team should give up on him as a starter just yet. The data says that the pitches are being hit much better than the quality of the stuff and I submit that it is lack of command leading to this conclusion.