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Mariners LHP Justus Sheffield
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Mariners progress report: How Seattle’s rookie arms have looked in 2020

Justus Sheffueld has been one of the Mariners' best young arms in 2020. (Getty)

One of the biggest keys to the Mariners’ 2020 season was the mantra of letting the kids play. The Mariners have accumulated a ton of young talent since general manager Jerry Dipoto and the rest of the front office decided to rebuild following the 2018 season, and the first major wave of young players has been on full display this season.

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Outfielder Kyle Lewis and shortstop J.P. Crawford have gotten a lot of attention this season due to their play both at the plate and in the field, while rookies Evan White and Shed Long Jr. have struggled offensively but continue to get opportunities to get through the cold spells.

The Mariners also have had a lot of rookies take the mound this season, and while it’s offered mixed results, it’s clear to see why Dipoto and company are excited about many of the young arms that have toed the rubber this season.

Let’s look at what Seattle’s youngest pitchers have done so far.

Starting pitchers

LHP Justus Sheffield

Stats: 2-3 record, 4.75 ERA, 1.319 WHIP, 29-12 K/BB, 30 1/3 innings in six starts

After two shaky outings to start the season (eight earned runs in 7 2/3 innings, seven strikeouts, six walks), Sheffield turned things around in a big way, throwing six innings in each of his next three starts and allowing a total of three runs.

Though he couldn’t make it through the fifth inning in his last start, Sheffield overall has been one of the Mariners’ better starters this season.

A big change for Sheffield from last year to now is the use of his two-seam fastball/sinker, which is sitting around 91 mph. He’s using that pitch 45.2% of the time per Statcast, as opposed to last year when he used a four-seam fastball 47.8% of the time. Opponents are hitting over .300 against the sinker, but Sheffield has avoided hard contact overall and has allowed just one home run and four extra base hits in 30 1/3 innings.

As expected, Sheffield’s big weapon has been his slider, which he throws 39.1% of the time and opponents are hitting just .157 against. All but six of his 29 strikeouts this year have come on the breaking ball.

Another good development has been the changeup, which he’s throwing about 15% of the time. It has about 5-6 mph of separation from his fastball and while he isn’t missing too many bats with it, opponents are hitting only .176 against it. Sheffield has always been known to have the good slider but a third pitch will be what keeps him in the starting rotation.

RHP Justin Dunn

Stats: 2-1 record, 4.33 ERA, 1.259 WHIP, 21-16 K/BB, 27 innings in six starts

Dunn, like Sheffield, has been pitching well of late and is coming off two consecutive outings where he’s thrown six innings of shutout baseball while allowing just one hit.

The big issue Dunn has run into in 2020 has been throwing strikes, as he’s walked nearly as many as he’s struck out. Even in his last outing where he allowed only one hit against the Angels, he walked four to go along with six strikeouts.

Something interesting with Dunn this year is, unlike many other pitchers, hitters aren’t hitting well off of his fastball. Opponents are hitting .104 on the heater according to Statcast, which is averaging 91.2 mph. Dunn is using that pitch 48.9% of the time. He’s also had good success with his slider, which he’s using on 14.4% of his pitches, as opponents are hitting only .160 off of it. And despite throwing it less than 15%, Dunn has more strikeouts with the slider (nine) than with any other pitch.

Where Dunn has gotten into trouble aside from walks has been with his curveball and changeup.

With the breaking ball, which he’s thrown on 23.6% of his pitches, opponents are hitting .353. Three of the five home runs Dunn has allowed are off the curve and opponents are slugging .941 against it. As far as the chanegup goes, Dunn has used it at a 9.8% rate and opponents have a .375 average against it.

RHP Ljay Newsome

Stats: 0-0 record, 2.57 ERA, 0.857 WHIP, 5-0 K/BB, seven innings in two appearances (one start)

We haven’t gotten to see a whole lot of Ljay Newsome this season, but he’s impressed in his two outings, allowing two runs in seven innings.

The main thing with Newsome is he pounds the zone. He’s thrown strikes 68% of the time in the big leagues and has yet to allow a walk. For those who have followed Newsome since the Mariners drafted him in the 26th round in 2015, that shouldn’t be a surprise. In five minor league seasons, Newsome has 473 strikeouts to 62 walks.

Newsome has mixed it up for the Mariners so far, throwing his fastball 45.7%, curveball 31.4% and changeup 22.9% according to Statcast. The curve has been the best pitch statistically, as he’s given up only one hit off of it.

Newsome joined the rotation due to the Taijuan Walker trade and Kendall Graveman’s injury, and even though Graveman was activated on Tuesday, it looks like Newsome will stick in the rotation while Graveman tries his hand out of the bullpen.

Not a rookie, but …

LHP Nick Margevicius

Stats: 1-2 record, 3.86 ERA, 1.13 WHIP, 23-5 K/BB, 25 2/3 innings in seven appearances (four starts)

Margevicius, 24, is not technically a rookie this season as he passed that requirement last season for the San Diego Padres, but he’s worth mentioning as he’s become a key part of this young Mariners team in 2020.

Originally starting the season in the bullpen, Margevicius became a starter after Graveman went on the injured list due to a neck injury. After throwing just 3 1/3 innings in his first start because he wasn’t quite worked up yet as far as his pitch count was concerned, Margevicius has made it into the sixth inning in his last three starts and finished the inning twice. In Houston on Aug. 15, he gave up just two runs in six innings in a 2-1 loss and in his most recent start against the Angels, same thing: six innings of two-run ball in a 2-1 loss.

Though a bigger guy at 6 foot 5, Margevicius sits at 90.3 mph with his fastball, which he uses over 60% of the time according to Statcast. He pairs that with a slider and curveball, and he mixes in the occasional changeup 6.4% of the time.

The slider and curve have both worked well for Margevicius, as opponents are hitting .182 off the slider and .200 off the curveball. There’s also a clear distinction between the two pitches, as the slider is firm at an average of 83.7 mph while the curveball averages 70 mph.

The young lefty is pounding the zone, throwing strikes 65% of the time and has walked just five batters in 2020. Not bad for a player the Mariners picked up off waivers in January from – guess who – the San Diego Padres.

Relievers

LHP Anthony Misiewicz

Stats: 0-1 record, 4.26 ERA, 1.184 WHIP, 17-3 K/BB, 12 2/3 innings in 12 appearances

Though the Mariners’ bullpen overall hasn’t been great in 2020, one of the better developments has been with Anthony Misiewicz, an 18th-round pick in 2015.

Misiewicz is missing bats, as evidenced throughout his Statcast page, with a strikeout rate of 32.7%, which ranks in the 87th percentile in MLB, and his whiff rate is in the 93rd percentile. The whiff rate is led by his cutter (39.3% whiffs) and curveball (47.8).

The cutter, which sits at just under 90 mph, has been Misiewicz’s go-to pitch, using it at a 49.5% clip, and opponents are hitting .259 off of it and have struck out eight times against it.

The curveball, used 27.1% of the time, has yielded similar results, with a .250 opponents’ batting average and registering eight strikeouts.

Misiewicz’s fastball, which averages 93.9 mph, has been used the least of his three pitches, and opponents have one hit off of it, and it was a single. It’s been thrown 23.3% of the time and has only ended plate appearances seven times.

RHP Joey Gerber

Stats: 0-0 record, 4.00 ERA, 1.00 WHIP, 2-3 K/BB, nine innings in 10 appearances

Joey Gerber, the team’s No. 20 prospect, has allowed four runs this season, but he has also allowed five of 13 inherited runners to score so far in his young MLB career.

He did start his career on a high note, recording a three-up, three-down inning against the Angels in his first appearance (watch that inning here).

Gerber uses both a fastball and sinker, both of which are around 93 mph, and his lone secondary offering is a slider, which he’s thrown 33.6% of the time according to Statcast.

Something that may be a little concerning is that Gerber, who struck out 112 batters in 74 2/3 career minor innings, has just two strikeouts so far in his big league career and has a whiff rate of roughly 13%. His strikeout rate of 5.6% is well below the MLB average of 21.7%.

His slider has had the best results so far, with opponents batting only .111 against it with no extra base hits.

LHP Aaron Fletcher

Stats: 0-0 record, 12.00 ERA, 3.000 WHIP, 3-5 K/BB, three innings in four outings

After three scoreless outings to start his MLB career, things got away from Fletcher, who the Mariners acquired from Washington at the 2019 trade deadline, against the Angels last weekend as he gave up four runs and got just two outs. A big issue was walks, as he had two that inning, giving him five in just three MLB innings so far. His strike rate so far is just 48% per Statcast.

Fletcher has good stuff from the left side that seems to fit well with his cross-body delivery that is especially tough on left-handed hitters, with a power sinker averaging 93.4 mph and using a slider as his put-away pitch while mixing in an occasional changeup.

Like many relievers, the slider is Fletcher’s out pitch, and already he has two strikeouts with it, has yet to allow a hit off it and has a whiff rate of 57.1% using it.

Like Gerber, Fletcher needs to show he can throw more strikes overall and miss more bats if he is going to be a reliable late-inning option for the Mariners going forward.

RHP Yohan Ramirez

Stats: 0-0 record, one save, 2.77 ERA, 1.462 WHIP, 21-14 K/BB, 13 innings in eight appearances

Hard-throwing right-hander Yohan Ramirez has been one of the more exciting Mariners pitchers to watch this year, with a hard fastball that averages 95.7 mph and he throws at a 63.3% clip, and a wipeout slider that has resulted in 14 strikeouts and zero hits that he’s used on 36.3% of his pitches according to Statcast.

A Rule 5 Draft selection this offseason from Houston, Ramirez had never appeared above Double-A before this season. As 710 ESPN Seattle’s Mariners insider Shannon Drayer has noted on her Twitter multiple times, the Mariners had been taking it slow with Ramirez, almost always putting him in at the start of an inning. That changed recently, as Ramirez worked a scoreless 10th inning against the Angels with a runner starting on second base, and he struck out two batters to get his first MLB save.

As was expected, control is the key issue for Ramirez, whose fastball-slider combination is very potent. He has walked more batters (14) than he has innings pitched (13), but his strikeout rate is in the 93rd percentile and, as noted, no one has gotten a hit off of his slider to date. Also of note, 11 of Ramirez’s 14 walks came in his first five outings. He has walked three in his last three outings, which totaled three innings, but he definitely seems to be finding the zone more than he was at the start of the season.

RHP Brady Lail

Stats: 0-0 record, 1.69 ERA, 0.938 WHIP, 7-3 K/BB, 5 1/3 innings in three appearances

Lail hasn’t pitched much since the Mariners claimed him from the White Sox, but in three outings, he’s given up just two hits and one home run, and that home run was to Mike Trout, so does it even count?

Lail, unlike most relievers, uses five pitches: fastball, curveball, slider, sinker and chanegup. The percentage Lail uses those five pitches goes in that order according to Statcast.

Interestingly enough, Lail has yet to give up a hit with four of his five pitches. Both hits he’s surrendered, including Trout’s home run, came off his slider.

Lail has been missing bats at a 27% rate, which is higher than the MLB average, so he has that working for him. He also has experience as a starter and has shown already he can go multiple innings for the Mariners.

LHP Taylor Guilbeau

Stats: 0-0 record, 1.17 ERA, 1.826 WHIP, 3-6 K/BB, 7 2/3 innings in eight appearances

Guillbeau is on the injured list and his season is over due to a shoulder injury, and while he personally only gave up one earned run in 7 2/3 innings, he also allowed three inherited runners to score. And though his ERA is just 1.17, Guilbeau allowed nearly two men to reach base per inning and walked twice as many batters as he struck out.

Something to note with Guilbeau this season was his velocity, or lack thereof. Per Guilbeau’s Statcast page, in 12 1/3 innings in 2019, Guilbeau’s average sinker and fastball were over 94 mph. In 2020, he essentially scrapped the fastball for the sinker, averaging 91.4 mph on the pitch. His overall whiff rate also dropped from an already low 19% last year to 13.5% and he threw first-pitch strikes just over 41% of the time.

Guilbeau’s secondary offerings of his changeup and slider had wildly different seasons as well.

With the changeup, which he threw over a quarter of the time, opponents ht .571 off of it with three doubles. Guilbeau didn’t give up a hit with his slider and recorded two strikeouts. He threw the pitch 16.2% of the time.

Follow 710Sports.com’s Brandon Gustafson on Twitter.

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