Player Profiles 2020: Seattle Mariners Starting Pitchers

Michael Ajeto analyzes the Seattle Mariners rotation for 2020 with in-depth player profiles.

Throughout the winter months of the offseason, the Pitcher List staff will be creating profiles for every fantasy-relevant player for 2020. Players will be broken up by team and role through starting pitchers, bullpen, lineup, and prospects. You can access every article as it comes out in our Player Profiles 2020 hub here.


Mariners At A Glance

Thankfully, the Seattle Mariners have an influx of talent in their starting rotation, because it’s been pretty underwhelming for a while now. Marco Gonzales teased us with a solid first half in 2018, Yusei Kikuchi looked like he could be a very solid starter, and Justus Sheffield and Justin Dunn both got a cup of coffee in 2019. Kendall Graveman isn’t without some promise, and he’ll look to give the Mariners’ rotation some stability. We could see a lot of good in 2020, but there is perhaps just as much potential for a whole lot of bad.


Marco GonzalesLocked Starter

Nickname: Gonzo


2019 In Review

After Gonzales excited me with a strong first half in 2018, his velocity gradually dropped throughout the year and he had an abysmal second half. I wrote about it as my first article at Pitcher List, but things have changed since then. His velocity hasn’t come back, and his strikeout and walk numbers have gone the wrong ways. Regardless, he finished with much worse peripherals, and yet a nearly identical ERA to 2018. His command is still intact, too.


Sinker (39% usage)

While Baseball Savant says Gonzales threw his sinker 39% of the time, FanGraphs’ source thinks he threw his sinker 674 times to his fastball’s 577. While I’ve generally been following Baseball Savant’s numbers, there’s a reason to split them up: his sinker is a ground ball pitch, while his fastball is a fly ball pitch. Regardless, I’ll lump them together here, as both don’t miss bats, nor are they good pitches. In 2019, Gonzales’ sinker and fastball put up a 5.3 SwStr% and 6.9 SwStr%, respectively.

His fastball gets a decent amount of whiffs when it’s elevated or to his arm-side, and his sinker isn’t bad when he pitches to those areas either. I wish he would elevate with his fastball more often.


Changeup (24% usage)

Over his career, Gonzales’ changeup has nearly been a Money Pitch, with a 40.8 O-Swing%, 37.8 Zone%, and 13.3 SwStr%. It just misses the mark. His whiffs have declined with it in the past few years, but maybe 2014 was a mirage — it has an obscene 25.4 SwStr%.

This is easily his best pitch — although his other secondaries have plenty of potential — as it’s been considered plus-plus since his college and minor league days. It’s a shame he doesn’t have a similar pitch — at least, by results — to go along with it.


Cutter (21% usage)

Gonzales hadn’t used a cutter at all until 2018 because of the pressure it put on his elbow. Now that he’s healthier, he’s been able to throw it with frequency. His SwStr% dropped considerably from 10.7% in 2018 to 6.9% in 2019, but it’s been his best pitch by xwOBA for two years now. By wOBA, it’s been his best pitch since 2018 too.

Considering it’s a new pitch, this is all quite impressive — especially since he has such a good changeup. It generates more weak contact than any pitch, and so if his sinker and fastball don’t improve, perhaps he could do the Wade Miley thing and use this as his primary fastball.


Curveball (16% usage)

This pitch declined considerably too, by SwStr% — it went from a 10.9% to a 7.4%. Of all of his pitches, Gonzales’ curveball has the worst Z-Contact%. So, why, then, does he throw it in the zone so often? If you look at where his whiffs come from, they’re generally below the zone, not in it. This is because Gonzales uses it often as a get me over pitch (it is pretty loopy), but I think he could use it as a swing and miss pitch sometimes, too.


2020 Outlook

Although there is a banality to this notion at this point, Gonzales is truly a crafty lefty and his plus command. He’s perhaps better suited than most to deal with a drop in velocity, but if he wants to be 3.50 to 4.00 ERA pitcher, he’ll need his velocity back. I’ll be watching, but with only the slightest bit of optimism — and because, as a Mariners fan, I’ll have to anyway. I could see something like a 4.40 ERA, 1.35 WHIP, and 18 K%.


Realistic worst-case projection: 4.50 ERA, 1.40 WHIP, 16% K rate in 160 IP

Realistic best-case projection: 3.80 ERA, 1.23 WHIP, 20% K rate in 200 IP


Nick’s reluctant Marco Gonzales 2020 projection:

4.20 ERA, 1.32 WHIP, 18% K rate in 180 IP


Yusei KikuchiLocked Starter

Nickname: The Stenographer


2019 In Review

There’s not a soul who is not disappointed in Kikuchi’s 2019. FanGraphs graded him as a 50 FV starter, but so far he looks like he’ll be lesser than that. Dating back to his time in Japan, he’s been interested in pitch design, and it sounds like he’ll be in contact with Trevor Bauer too. Regardless, there’s reason to think that that seam changes on the ball affected him more than others, so his future may be less than previously thought.


Fastball (49% usage)

Kikuchi’s fastball was…so…bad. It returned a -16.0 pVAL and -1.2 pVAL/C, with a 6.8 SwStr%. It seemed to be the case with most of his pitches, but Kikuchi was getting squeezed badly on his fastball. Thus, he might have been forced to throw it over the plate more. It’s unclear whose fault this is — I imagine it’s a combination of poor command, catcher framing, and something about him — but regardless, it’s unjust. That’s why I can’t criticize him, because this could potentially ruin everything for him.

Regardless, his fastball pretty universally received a 50-grade, and his velocity ranks in the 41st percentile, while his fastball spin ranks in the 15th percentile. His inactive spin is bad, too. Maybe...just throw a cutter, Yusei.


Slider (28% usage)

His slider was easily his best swing and miss pitch, and, despite receiving a worse 55-grade on his slider and a 60-grade on his curveball, it was his best pitch on the year. All hope isn’t lost for Kikuchi, as his slider essentially graded out as a Money Pitch, with a 43.6 O-Swing%, 42.4 Zone%, and 14.8 SwStr%.

Relative to league average, his slider had an elevated wOBAcon and BABIP, so perhaps those will come back to earth next season, but if hitters are just trying to sit on his breaking pitches, that may not be true. Regardless, his wOBAcon exceeded his xwOBAcon, so there’s a chance this pitch looks better next year.


Curveball (15% usage)

As I said, FanGraphs gave this pitch a 60-grade. I don’t know why, honestly. It’s big, slow, and loopy, and it doesn’t attract whiffs. Seriously, it had a SwStr% of 4.0%. 4.0%! He mostly used in 0-0 counts and sparingly when he was ahead. He pretty much never used it when he was ahead, because it’s purely a get me over curveball that he throws in the zone.

It has the highest Strike% of all of his pitches at 35.6%, which is because of the way that he uses it. If he were to bury it beneath the zone, it might get more whiffs, but it still wouldn’t be good. It doesn’t play well there, so Kikuchi either needs to lessen the use of his curveball, find a new grip, or scrap it completely. I love you, Yusei, but this pitch is just not good.


Changeup (8% usage)

This pitch showed some promise is 2019. It’s still a work in progress — it seems to be the pitch that he wants to hone the most — but it’s not there yet. Along with his slider, it at least gives him some hope to have a solid repertoire. His changeup checks in with a 35.3 O-Swing%, 33.2 Zone%, and 10.1 SwStr%. Not great, but not bad.

By wOBA, it was his best pitch, but by xwOBA, it was tied with his slider. Of course, his slider is obviously the superior pitch, but this is something that won’t get beat up by like fastball and curveball do.


2020 Outlook

Given his 2019 numbers, there’s nothing about Kikuchi to be optimistic about. However, I have a feeling he’ll get into some pitch design this offseason. I recall seeing that he was interested in pitch design while in Japan — and he reached out to Bauer, too — and then you have the changes he endured with the ball from Japan to ball in the United States. It’s safer to be pessimistic with Kikuchi than optimistic, but on the high end I see a 4.20 ERA with a 1.30 WHIP and 20 K%, but on the low end a 5.10 ERA with a 1.50 WHIP and 16 K%.


Realistic worst case projection: 5.00+ ERA, 1.50+ WHIP, 16% K rate in 130 IP

Realistic best-case projection: 4.20 ERA, 1.30 WHIP, 20% K rate in 190 IP


Nick’s reluctant Yusei Kikuchi 2020 projection:

4.80 ERA, 1.37 WHIP, 18% K rate in 175 IP


Justus SheffieldLikely Starter

Nickname: Top Sheff


2019 In Review

Acquired in a trade for James Paxton, Sheffield started the year in Triple-A but struggled so mightily that he was demoted to Double-A. His command improved upon his demotion, and he eventually appeared in eight games for the Mariners. However, it wasn’t too encouraging, as he finished his stint in the majors with an 11.3 K-BB%, 123 ERA-, 105 FIP-, and 102 xFIP- in 36.0 innings.


Fastball (48% usage)

Perhaps as problematic as his command issues is that Sheffield has a really poor fastball. By fastball velocity, it ranks in the 48th percentile, so it’s basically average — but in fastball spin, in ranks in the 0th percentile. To make matters worse, it has a 64.1% active spin, which ranks in the 5th percentile. So, to recap: average velocity, awful total spin, and awful active spin derived from his awful total spin.

By movement, it’s basically a sinker because it’s such a heavy fastball. By vertical movement, Sheffield has the 335th least vertical movement out of 348 pitchers. By horizontal movement, it’s not as bad. On the year, Sheffield threw it to the vertical middle of the zone, on average. It seems to play up a little more at the top of the zone, but the sample is so, so small, so it’s hard to make any conclusions about where his fastball plays best.

Overall, his fastball garnered a 4.4 SwStr%, with a -2.1 pVAL and -0.7 pVAL/C. The bad news is that, by batted ball quality, he overperformed the league average xwOBAcon. But, according to Alex Chamberlain’s Tableau, his K% and BB% on the pitch are expected to regress in the right direction.


Slider (36% usage)

Sheffield’s slider is sick. With a 40.1 O-Swing%, 34.3 Zone%, and 23.9 SwStr%, it’s just shy of a Money Pitch — he doesn’t throw it in the zone enough to qualify. His slider plays extremely well to his glove-side and beneath the zone. It plays so well that, for starters, Sheffield’s slider ranks 8th in the league in SwStr% — it’s legit.

This pitch got hit really, really hard. That probably has to do with a few things. First, his command isn’t great. Second, he doesn’t have a serviceable fastball. Lastly, pure bad luck and small sample size. That explains why his -3.6 pVAL and -1.5 pVAL/C are even worse than his fastball. This pitch should get better. It’s nasty.


Changeup (16% usage)

Sheffield has been trying for years to develop his changeup. The good news is that he may have done that. There’s a lot of discussion about what makes a good changeup. A healthy velocity differential between one’s fastball and changeup is pretty much always good. However, there are certain combinations of drop, velocity, and movement that don’t work well. He was said to be happy with his changeup, so that’s encouraging as well.

Importantly, his changeup was good this year, albeit in a small sample. Over 112 pitches, his changeup garnered a 37.8 O-Swing%, 33.9 Zone%, and 15.2 SwStr%. Again, that qualifies for the two most important criteria (in my opinion) for a Money Pitch. By pVAL, this was his best pitch on the year, accruing a 0.9 pVAL and 0.8 pVAL/C.


2020 Outlook

I just cannot get excited about Sheffield until I’m more optimistic about his fastball. As is, I think he has strong enough secondaries to be serviceable, but as a starter, he’s shaping up to be something like Dylan Bundy or the Pirates version of Chris Archer. Bad fastball, plus-plus slider, solid (or better) changeup. And with that, Sheffield also has durability and command concerns, too. Not ideal. I can see a 24 K%, 9 BB%, 1.40 WHIP, and 4.45 ERA being realistic and attainable.


Realistic worst-case projection: 4.90 ERA, 1.45 WHIP, 10% K rate in 110 IP

Realistic best-case projection: 3.90 ERA, 1.27 WHIP, 25% K rate in 180 IP


Nick’s reluctant Justus Sheffield 2020 projection:

4.40 ERA, 1.35 WHIP, 23% K rate in 140 IP


Kendall GravemanLikely Starter

Nickname: Tombstone


2019 In Review

Graveman had Tommy John surgery and missed the part of the 2018 season and the entire 2019 season, with a combined six innings in rookie league and Triple-A.


Sinker (56% usage)

Back in 2017, Jeff Sullivan (formerly of FanGraphs) wrote about Graveman’s spiking sinker velocity. He added on by comparing his sinker to Aaron Sanchez’s, which isn’t as much of a co-sign nowadays. Of course, it is decidedly not 2017, and Graveman has not shown the development with his sinker that was envisioned. After seeing his velocity jump to nearly 95 mph, it was back down to about 94 mph in 2018.

Over his career, his sinker has accumulated a 2.3 pVAL and 0.1 pVAL/C, so it’s not a bad pitch despite its 5.1 SwStr%.


Changeup (15% usage)

With a 43.9 O-Swing%, 29.8 Zone%, and 18.1 SwStr%, Graveman’s changeup took a step forward from his career 39.0 O-Swing%, 31.2 Zone%, and 10.4 SwStr%, albeit in a rather small sample. He started throwing it to righties a touch more in 2018, but the big changes came from an uptick in swing and misses from lefties — this appears to be from impeccable changeup placement. It’s unclear if this is sustainable, but if he is able to spot this consistently low and away from lefties, it’s going to be difficult for hitters to do anything with it. The downside is it doesn’t have ideal velocity differential or horizontal separation from his sinker.


Cutter (14% usage)

Graveman has one of those funky cutters that have arm-side movement (which is atypical), but it doesn’t move like a four-seam fastball or a sinker. It has far less arm-side movement than a four-seamer, but much more vertical drop than both his sinker and four-seam fastball, as well as less velocity. Essentially, the pitch has David Price cutter movement (running from left-to-right), but it’s coming out of the arm slot of a righty.

With a career 34.0 O-Swing%, 41.6 Zone%, and 11.7 SwStr%, Graveman’s cutter looks like a solid pitch, but it has also accumulated a -11.1 pVAL and -0.8 pVAL/C, making it easily his worst pitch.

Slider (13% usage)

Graveman’s slider is something in between a curveball and slider. It has the velocity and movement profile of a curveball, but its active spin resembles both a curveball and slider. Despite being his least-used secondary pitch, it’s perhaps his best.

It has a career 34.8 O-Swing%, 44.4 Zone%, and 10.6 SwStr%. Paired with a 2.3 pVAL and 0.4 pVAL/C, he may be well suited by throwing it more than his cutter.


2020 Outlook

Unfortunately, Graveman fits in all too well with the Mariners pitching staff. With the balls being as bouncy as they’ve been he should be well suited with his ground ball-heavy profile, but it’s hard to envision a meaningful increase in strikeouts, and his durability is a question mark. I think his Steamer projections of a 4.78 ERA, 1.40 WHIP, and 17.3 K% look about right.



Realistic worst-case projection: 5.00+ ERA, 1.45 WHIP, 14% K rate in 80 IP

Realistic best-case projection: 4.20 ERA, 1.30 WHIP, 18% K rate in 180 IP


Nick’s reluctant Kendall Graveman 2020 projection:

4.50 ERA, 1.40 WHIP, 15% K rate in 140 IP


Justin DunnLikely Starter

Nickname: One Second Egg Timer


2019 In Review

Before this season, Dunn didn’t seem to be more highly touted than Sheffield, but he should be now. He had the more impressive overall 2019, and while he looked lost when he got called up, he pretty visibly had some nerves to work through that should, theoretically, subside with more exposure to the bigs. Dunn put up a 21.5 K-BB% in AA, which went seemed to fly under the radar.


Fastball (57% usage)

At the major league level, he only threw 80 fastballs, but they weren’t great. His control of his fastball was shaky, and he didn’t miss very bads, with a 90.9 Contact % and 2.5 SwStr%. However, as I said, he had some nerves, and the sample is really small.

There are some encouraging factors, though. Of all fastballs thrown by starters 50 times or more, Dunn’s fastball ranked in the 72nd percentile in fastball spin, paired with an 88.6% active spin rate, which ranks in the 72nd percentile. Lastly, his fastball velocity ranked in the 52nd percentile. Of course, he pitched in more of a pseudo-starting role, so we could see his fastball velocity and spin both drop, but it’s much easier to feel confident in him than Sheffield.

By fastball movement, his fastball has decent ride, and has some rise too. It ranks in the 90th percentile in rise, per Baseball Prospectus, and in the 77th percentile according to QOP Baseball. By movement profile and velocity, a few quick comps for his fastball might be teammate Erik Swanson — he is pretty highly regarded as a plus spin guy who can pitch fastballs up and everything else down — and Jose Urquidy. While it seems like his fastball could be good on paper, some of the players who throw vaguely similar fastballs make me more uncertain. In any case, FanGraphs has his fastball grade at a current-55, and Baseball Savant has him at a current-60 grade.


Slider (35% usage)

This is Dunn’s best secondary pitch. Although his command overall is below-average, he commands his slider very well. In just 47 pitches (so take it with a grain of salt), he had an O-Swing of 39.3%, Zone% of 40.4%, and a 12.8 SwStr%. That’s Money Pitch territory!

His slider is more of a horizontal pitch than vertically breaking pitch, so he mostly throws it to the bottom of the zone (or below) on his glove-side, rather than throwing it below the zone in general. I find that it’s easier to have success with a slider with drop rather than big horizontal movement, but Dunn’s slider is great.


Changeup (18% usage)

Dunn barely threw his changeup last year, but it’s said to flash plus, although scouting grades differ on the pitch. He didn’t get any whiffs on it, but he’ll need it to get lefties out. His fastball-changeup velocity differential isn’t great, and its arm-side movement is only slightly above-average, but it separates itself from his fastball well.


2020 Outlook

I hope he can figure his fastball command out because I really like Justin Dunn. There are sure to be some hiccups — probably a lot of walks and too many home runs — but I expect him to show a lot of promise and lock up a starting rotation spot (although he’s not absolutely certain to). Something like a 4.40 ERA, 1.40 WHIP, 22 K%, and 9 BB% is absolutely attainable for him.


Realistic worst-case projection: 4.75 ERA, 1.45 WHIP, 20% K rate in 50 IP

Realistic best-case projection: 4.00 ERA, 1.30 WHIP, 25% K rate in 160 IP


Nick’s reluctant Justin Dunn 2020 projection:

4.40 ERA, 1.35 WHIP, 23% K rate in 150 IP


Ljay NewsomeFringe Starter

Nickname: The Story Teller


2020 Outlook

After attending a gas camp to improve his velocity, Newsome saw his velocity improve by about 6 or 7 mph and overpowered hitters for half of a season before receiving a call-up to Double-A. He saw his K% drop from 30.4% to 18.5%, but I’m still a huge fan and think we’ll see him adjust in 2020. He’ll probably get some major league reps by the end of the year.


Erik SwansonFringe Starter

Nickname: Final Chapter


2020 Outlook

It’s looking more and more like Swanson is going to end up in the bullpen, but he still has a shot at earning a rotation spot. After the James Paxton trade, Jeff Sullivan noted that Swanson performed better than Justus Sheffield from Double-A to Triple-A. His fastball velocity and fastball spin rate don’t jump off the page, but his fastball has great perceived rise, thanks to a 93.0% active spin rate. The fastball was great, but he needs to develop his slider or changeup (but probably both).



Marco GonzalesGonzo. You don’t need me for this one.

Yusei Kikuchi: The Stenographer. He tells you what you said (he says this, you say that).

Justus SheffieldTop Sheff. Like the cooking show.

Justin Dunn: One Second Egg Timer. Because he’s Just Done…Done.

Kendall GravemanTombstone. He’s a grave man. He’s just really into graves.

Ljay NewsomeThe Amnesic Story Teller. When you ask him if he knows any stories, he says “yeah, I knew some.”

Erik SwansonFinal Chapter. His last name sounds like “Swan Song”, i.e. someone’s last hurrah

Featured Image by Justin Paradis (@freshmeatcomm on Twitter)

Michael Ajeto

Michael writes about the Mariners at Lookout Landing, as well as here at Pitcher List. You can follow Michael on Twitter @dysthymikey, or you can not.

4 responses to “Player Profiles 2020: Seattle Mariners Starting Pitchers”

  1. Shawnuel says:

    You don’t think Logan Gilbert will be up in the final month or two?

  2. Michael Ajeto says:

    Steamer doesn’t have him pitching much in the majors in 2020, but I will say that I am more optimistic that he sees some time by the end of the year. Perhaps I’ll think about adding him.

    I think of all of the starting pitchers from Double-A to the majors, he excites me the most. He’s the most polished, and he’s quite underrated, in my opinion. I see no reason why he shouldn’t get a few September starts unless this year is a disaster.

  3. Brian Fawcett says:

    Can we just have less on the silly nickname stuff, and more on the analysis side? This is useful work you’re doing, but no one needs the creative writing dept. slop

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