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Projecting the Mariners’ 26-man roster: Pitchers

Can a promising rotation ease fears about a suspect bullpen? You decide.

San Diego Padres v Seattle Mariners Photo by Steph Chambers/Getty Images

Spring has sprung, the cherry blossom trees are blooming in full force, and if you can believe it, we are just six days away from Opening Day. Has spring training felt longer this year than normal? Matthew thought so the other day, and I’m inclined to a agree. Anyway, Scott Servais hinted on Sunday that the Mariners would finalize their 26-man roster sometime over the weekend, likely during the weird, well-earned (seriously, they’re playing twenty-six straight games without a break) off-day the club has on Sunday. Several spots were locked up before pitchers and catchers reported, but a few battles for second base, left field, and that sixth rotation spot have raged on. As we near the end of the Cactus League, things appear to be pretty well shaken out, and while it may just be the inherent optimist in me, it’s pretty easy to squint and see an intriguing team that could surprise some folks through the summer. On Wednesday, we profiled the group of position players who should make the Opening Day cut, and today we’ll meet the six starters and eight relievers that will most likely join them.


Marco Gonzales, LHP

After delivering two solid full seasons with the Mariners with varying levels of uncertainty about how long he could keep it up, Marco kicked it up a notch in 2020. His 2.5% walk rate was tied with Kyle Hendricks for the lowest in baseball, he ran a strikeout-to-walk ratio of over 9:1, and he worked deep nearly every time he took the ball - he failed to make it through five full innings just once across eleven starts. His cutter has developed into a deadly offering against righties, and his slow curveball started coaxing more whiffs out of opponents’ bats. Unquestionably the ace and leader of the rotation - as well as in the clubhouse - we maybe shouldn’t expect a full year with Mariner Cliff Lee-level command, but there is no doubt that Marco has snuck under the radar to become one of the best arms in the American League, and there’s a chance he could receive some Cy Young votes come November.

James Paxton, LHP

It is a joy to have James Paxton in a Mariners uniform once again - and if you were wondering, the Maple Grove will be back, initially in virtual form to start the season. Check out their website for more information and merchandise; they are friends of the site and have some big things planned this year!

There was some concern that Paxton was nursing an injury after it took him nearly a month to get to throwing in an actual Cactus League game, but thankfully we got confirmation that it was merely a work visa issue. Those wacky Canadians! Any doubts about a dip in velocity or stuff were quickly assuaged on Sunday, thanks to a dominant outing from James featuring eight strikeouts, including a Christian Yelich flail through 96:

As always, health will be the question for Paxton. He was out for a good chunk last year with a flexor strain, continuing a nigh career-long stretch of missing some time each season to injuries. Seattle’s six-man rotation should help avoid the strain on his arm, however, and a healthy Big Maple is a big boost to a promising group of starters. Although there’s a good chance he’ll be flipped at the deadline should the M’s fall out of contention, he’ll be a source of fun for every minute he’s here, and the return of the Grove is just another element of normalcy coming back to the world.

Justus Sheffield, LHP

Coming off of a 2019 in which he showed glimpses of why he was the headliner of the James Paxton deal in 2018, Justus was quietly very effective in his first “full” season. Although he didn’t grab any Rookie of the Year votes, he had the highest fWAR among all rookie pitchers in the American League, and only trailed the Dodgers’ Tony Gonsolin overall. For the second straight year, he put up a ground ball rate north of 50% - always a good ingredient for success to have - but this time around, he avoided a lot of damage via long ball, giving up just two homers over 55.1 innings. For reference, in 2019 he gave up five home runs in nine fewer innings; quite the turnaround.

In 2020, he swapped out an ineffective four-seam fastball in favor of a sinker, which could explain his newfound ability to keep the ball in the yard, and his changeup has continued to develop alongside his wipeout slider. His command could still use a little polishing, but he cut his walk rate down two points from 2019, and that’s a trend I can see continuing for him into 2021. Health permitting, he should be a stalwart in the Mariners’ rotation, and as he’s entering his age-25 season, there’s still a chance he could become even better.

Yusei Kikuchi, LHP

Don’t let last year’s high ERA fool you - the Yusei Kikuchi we saw in 2020 was miles better than the one we saw in 2019. His fastball zipped in at average of 94.9 MPH, though he actually threw his lethal, Paxton-esque cutter more often. He did walk a few more batters than in his first season, but when you can trade that for an eight-point bump in ground ball rate, a full two-run drop in FIP, and most importantly for Yusei, halving your HR/FB, you take that every time. The 5.17 ERA can be at least partially explained by some bad sequencing luck (just a 59.9% strand rate last year), and there’s a good chance that swings back up this season, and he’ll need to deliver consistently good results for Seattle to pick up his option for 2022.

There’s another wild card for Kikuchi this year, though, and that’s the increased crackdown by MLB on pitcher grips such as pine tar. While many fans and players seem not to consider it an issue, the fact remains that Yusei uses it, and has never made much of an attempt to hide doing so. It remains to be seen exactly what disciplinary actions will be taken for violation of the new rules, but it could have not-so-good effects for a pitcher who’s already struggled with command early in his big leagure career. Guess we’ll find out!

Chris Flexen, RHP

It was one of the last moves the club made before going into hibernation for nearly two months over the offseason, but I’m still bullish on the Chris Flexen signing. After three years of riding the AAA-MLB shuttle with the Mets - and disastrous results in the Majors - Flexen reinvented himself in the KBO, and returns stateside as one of the few starting pitchers that was fully stretched out the year before.

Armed with a fastball sitting 92-93 that he loves to work high in the zone with, a sharp curve in the high 70s, and a solid changeup, Flexen should find a home somewhere in Seattle all season, whether that’s in the rotation should he get into an early groove, or in the bullpen in a swing role once highly touted pitching prospect Logan Gilbert is ready to break into the bigs. He’s here on a two-year deal, too, which could make him either an attractive trade chip at the deadline or a strong option to hold onto for depth in 2022. It’s always fascinating to follow how a playing returning to MLB from Korea or Japan perform, and I look forward to seeing him cast aside his previous failures as a Met.

Justin Dunn, RHP

Despite a fierce battle for the last rotation spot between Justin Dunn and Nick Margevicius, I think Dunn will pull ahead to start the year. His fastball has shown plenty of life that wasn’t present in 2020, routinely touching 96, and his breaking ball looks much more sharp and lively than it had before.

Of course, there’s still some red flags to keep an eye on. Command has remained an issue for Dunn, and nine walks over 11 spring innings have done little to quell those concerns. His durability is also still a concern; after cruising through the first three innings of his final Cactus League start on Wednesday, he fell apart in the fourth, walking two and allowing a homer and triple. I have to imagine that Dunn will be kept on a pretty short leash, both in pitch-count and chances to prove he’s taken a step forward, and if his struggles with control continue, a ticket to Tacoma or the bullpen could be on his doorstep pretty quickly - should starting not work out, those three-inning bursts of effectiveness could be a killer relief option. For now, though, the clear uptick in stuff and being right-handed in a lefty-heavy rotation should give him the edge over the lower-ceiling Margevicius, even if the latter is a surer bet to go deeper into games - but don’t be too surprised if we see Marge in this spot come Memorial Day.


Rafael Montero, RHP

Acquired from Texas for minor league outfielder José Corniell, the move to get Rafael Montero was met with a mixed reaction. Some weren’t a fan of what appeared to be an early era Dipoto trade - that is, trading away raw, toolsy, highish ceiling prospects for a higher floor, lower ceiling player that’s closer to the Majors - but Montero should be a solid contributor in the bullpen this year, and still has another year of arbitration before hitting free agency. He brings a fiery fastball that averaged just a hair under 96 last year, a changeup against lefties that gets plenty of whiffs, and a slider that sits at around 86 that is a good separator against same-handed hitters. Once a top pitching prospect for the Mets, he served well as the Rangers’ closer in 2020. He should occupy that same spot to open the year in Seattle, and there’s no real reason to suspect a sudden collapse from him (well, you know, other than injuries, and Montero underwent Tommy John in 2018. Quick, find some wood!)

Kendall Graveman, RHP

He’s only been with the M’s for a season and change, but Kendall Graveman has had a wild ride in his time here. Coming off of Tommy John in 2019, he entered 2020 as a prime bounceback candidate in the rotation - his fastball had newfound life and sink, and striking out the side in order in the first inning of his Mariner debut was a hell of a first impression. Unfortunately, he hit the injured list following his second start, where it was revealed that he had a benign bone tumor in his neck that can’t be safely operated on. As scary as that sounds, Graveman embraced becoming a full-time reliever, and was very effective in his new role, throwing a scoreless outing seven out of nine times. More importantly, however, is that he’s had no arm issues since coming over here. He also emerged alongside Kyle Seager and Marco Gonzales as a clubhouse leader when the Kevin Mather fiasco hit, and his and Montero’s veteran status should bring some stability to a bullpen with plenty of young arms waiting in the wings. He figures to occupy a setup role to start off the year.

Anthony Misiewicz, LHP

Here’s another guy who’s had a bit of a wild ride as a pro: after drafting him in the 18th round in 2015, the Mariners traded Anthony Misiewicz with Luís Rengifo to Tampa Bay in August 2017 for Mike Marjama and Ryan Garton - only to reacquire him four months later for slot money after the failed bid for Shohei Ohtani. Back with the M’s, he had a rough 2018 in Double-A, but was able to right the ship the next year - even relatively conquering the lunar run-scoring atmosphere in the Pacific Coast League - and found himself on the Opening Day roster in 2020. Wild stuff!

The unassuming Misiewicz was one of Seattle’s most reliable relievers last year; making his debut on Opening Day, he led the pitching staff with 21 appearances. Righties were a bit of a problem for him, but he shut down left-handed hitters, and generated a good amount of swinging strikes from all three of his cutter, fastball, and curve. The traditional LOOGY isn’t really a thing anymore, but we could see him in the seventh or eighth innings paired with Graveman fairly often, especially if a rash of lefties are due up.

Joey Gerber, RHP

It’s a safe bet that what we saw from Joey Gerber in 2020 isn’t reflective of his overall talent. It was maddening and headscratching to see his strikeout numbers completely dry up from the excellent marks he put up all through the minors, but the theory that he was down a tick or two in velocity all season seems to have held water.

Gerber’s enjoyed a pretty strong stretch in the Cactus League - one four-run egg laid notwithstanding - and more importantly, his strikeouts are back, with ten across 7.1 frames. If that 95-96 stays constant in the regular season, that 9.7% K-rate he managed last year is nearly guaranteed to go up, and nothing in his profile suggests that will come at the expense of extra walks. He’ll likely be kept out of many high-leverage situations to start the season, but could see plenty of work in the middle innings, and may be tapped on occasion to get four outs. In any case, we can expect his Twitter feed to remain full of wit.

Keynan Middleton, RHP

Another small, though still Major League signing Seattle made this offseason, Middleton has had a bit of a rough spring - though an outing where you give up three home runs in one inning has a way of skewing things in March. He’d spent the previous four seasons with Anaheim, with some mixed results - a solid rookie showing in 2017 gave way to injuries and command issues, and ruffled some Angels’ fans feathers with some snark about their enthusiasm. Honestly, any shade thrown towards that organization will make me like a player that much more. Middleton does have an option remaining, per Goose’s payroll, so there’s some flexibility there if he struggles, but at full health, his 97 MPH fastball should be the hottest velocity in a bullpen that is full of it.

Casey Sadler, RHP

Arriving via a waiver claim from Chicago last September, Sadler was a decent arm for the M’s down the stretch - a 3.29 FIP is certainly nothing to sneeze at. After Graveman, Montero, and Middleton, he’s the arm with the most Major League experience in the M’s bullpen, tossing 85.1 innings across parts of five seasons with the Pirates, Rays, and Dodgers, Cubs, and Mariners. Sadler brings a high-spin curveball at 80-81 that he actually used as his primary pitch last year, which he pairs with a sinker and occasional cutter. As a 30-year-old journeyman, he might be one of the first arms on the chopping block should ineffectiveness strike, but for now, he’ll be another option for any middle innings that need work.

Will Vest, RHP

It’s been peaks and valleys for Will Vest this spring, but he stands a good chance at being the third straight Rule 5 pick by the Mariners, after Brandon Brennan and Yohan Ramírez, to make the Opening Day roster. Like Brennan, Vest brings a mind-bending changeup that falls off the table, and his fastball has been sitting in the 94-95 range lately; in fact, he caught Matt Chapman looking with 95 on the black in yesterday’s game. He also throws a slider, but that pitch lags far behind the changeup as his go-to offspeed offering. Although he’s never started a game at the professional level, he’s capable of going multiple innings, as evidenced by his career 132.1 inning pitchers over 88 appearances in the minor leagues. Like nearly every Rule 5 pick, it’s likely the club will shield him from any spot with more than a crumb or two of leverage, but if he performs well in mop up or blowout duty, he could earn a more consistent and trusted spot in the ‘pen, assuming they keep him all season.

Aaron Fletcher, LHP

This last spot could conceivably be filled by Erik Swanson or the loser of the Dunn/Margevicius battle, but I have a feeling Aaron Fletcher has the inside track. Margevicius (yeah I’m rolling with this assumption) likely wouldn’t benefit from hanging out in a long relief role, and while Swanson has put up a nice spring, I think the club would prefer to have a second lefty in an eight-man relief corps. Fletcher made his Major League debut last season, and while command was a struggle for him over 4.1 innings, he still has plenty of promise at 25. His three-quarters arm angle could make him a deadly arm against lefties; he frustrated Jarred Kelenic at the alternate site all season last year. His low-80s slider features plenty of drop and lateral movement, and his sinker has allowed him to run strong ground ball rates through most of his pro career. He’s another guy who has a minor league track record of being able to go multiple innings, but I think Seattle would limit him to just one frame at a time, as a treat.


A longtime tradition of mine in the offseason is writing out on pen and paper what the Mariners’ 25-man roster would look like if the season started the next day, with revisions throughout the winter following. I’ve done this for about as long as I can remember avidly following the team, though Twitter records will show this has only been an annual thing since 2016. I noticed some disappointment in Wednesday’s comments that I neglected to include it with the position players, so here is a gift from me to you, with batting order and everything! Without further ado, if the 2021 season started tomorrow...

Go M’s.