2024 Seattle Mariners Pitching Preview (2024)

SP Luis Castillo

2024 Seattle Mariners Pitching Preview (1)

Castillo went from a breakout ace to a painful ride in 2021. He led the National League in walks (75), creating plenty of WHIP risk (1.364). When the lights turned on opening day, his arm dug an early hole for fantasy teams (eight runs, 10 baserunners, and one home run over 3.1 innings).

After 11 starts, Castillo went 1-8 with a 7.22 ERA, 1.777 WHIP, .321 BAA, and eight home runs over 52.1 innings. He gained momentum over his next 12 games (5-2 with 1.91 ERA, 1.115 WHIP, .199 BAA, and 80 strikeouts over 75.1 innings). Castillo blew up again on August 9th (eight runs, 10 baserunners, and two home runs over 3.1 innings). His season ended with a 2.70 ERA, 1.218 WHIP, and 62 strikeouts over 56.2 innings.

In essence, Castillo pitched well over three-quarters of the season (3.05 ERA) while still delivering too high of a WHIP (1.257). Most of his command issues came against lefties (54 of 75 walks over 347 at-bats).

In 2022, he started the year on the injured list with a right shoulder issue. Castillo threw the ball well over his 14 games with the Reds (2.86 ERA over 85 innings with 90 strikeouts). His arm had a slight step back after a trade to Seattle (3.17 ERA and 77 strikeouts over 65.1 innings). He finished the year with a lower walk rate (2.7) while posting strength in his strikeout rate (10.0).

Other than some issues with home runs (1.3 per nine) in 2023, Castillo has been an excellent addition since arriving in Seattle. He allowed two runs or fewer in 19 of 33 starts. His season ended on a down note in September (4.96 ERA over 32.2 innings) due to an increase in walks (18) and home runs (5). Despite success vs. lefties (.229 BAA), Castillo allowed 20 home runs over 388 at-bats.

His average fastball (96.4) was a four-year low but remains an elite offering (four-seamer – .165 BAA). Castillo saw his top two secondary pitches (changeup – .276 BAA – .227 in 2022 and slider – .188 BAA – .238 in 2022) lose some value. He changed his approach again to batters, leading to a much lower groundball rate (38.9 – 50.1 in his career) and a much higher flyball rate (42.4 – 31.1 in his career).

Fantasy Outlook: Castillo was the fifth-best starting pitcher in 2023 based on FPGscore (5.60) for pitchers. His ADP (30) ranks him as the 6th starter selected in the NFBC in early February. The Mariners are an improving team, and Castillo fits the profile as an ace. This season, he must find a balance between pitching up in the strike zone to lefties and keeping the ball in the ballpark. The regression in this area also came via his changeup (.285 with five home runs over 123 at-bats). Not quite a lock, but there is still room for growth.

SP George Kirby

2024 Seattle Mariners Pitching Preview (2)

Seattle snatched up Kirby with the 20th selection in the 2019 June Amateur Draft. He dominated over his final two years in college (18-5 with a 2.82 ERA and 203 strikeouts over 178.2 innings). His highlight stat came in 2019 when he walked only six batters over 88.1 innings.

The Mariners gave him nine appearances at Low A 2019, leading to a 2.35 ERA and 25 strikeouts over 23 innings while not walking a batter. In 2021, Kirby breezed through High A and AA (5-3 with a 2.53 ERA and 80 strikeouts over 67.2 innings) while missing some time midsummer with a left shoulder issue.

Seattle gave Kirby six starts in the minors in 2022 (2-1 with a 3.04 ERA, 1.050 WHIP, and 34 strikeouts over 26.2 innings). With the Mariners, he struggled in three of his first 10 starts, leading to a 4.08 ERA, 49 strikeouts, and 12 home runs over 53 innings. His future upside shined over his next 12 games (5-1 with a 2.09 ERA, 1.036 WHIP, .241 BAA, and 74 strikeouts over 64.2 innings). Unfortunately, he tripped up over his final three appearances (10 runs, 25 baserunners, and 10 strikeouts over 12.1 innings).

In his sophom*ore year with the Mariners, Kirby led the American in walk rate (0.9 per nine) while upping his inning total to 190.1. His elite strike-throwing didn’t result in more strikeouts (8.1 per nine). He had four disaster games (23 runs, 38 baserunners, and eight home runs over 17.1 innings) over his first 20 starts while also having a rough patch over six matchups (21 runs, 44 baserunners, and seven home runs over 34.0 innings). Kirby allowed two runs or fewer in 17 starts.

His average fastball (96.2) has an uptick in velocity. Batters only hit .231 against his four-seamer. Kirby added a split-finger fastball (.143 BAA with 20 strikeouts over 173 pitches). He still doesn’t have another difference-maker pitch (sinker – .261 BAA, slider – .259 BAA, and curveball – .265 BAA).

Fantasy Outlook: Sometimes, in fantasy sports, a drafter has to bet on the come and take a stance on a player. Kirby fits into that realm in 2024. He finished 10th in FPGscore (4.21) for pitchers last season while drawing a seventh ranking by ADP (39) in the early draft season in the high-stakes market. He had a bump in his strikeout rate (9.0) after the All-Star break, helped by the addition of his split-finger pitch. His command sets the tone for a massive edge in WHIP, and Kirby looks on track to post a sub-3.00 ERA. I’m feeling 225 strikeouts with 200 innings pitched, with a chance to kick that door down if any of his breaking pitches move to elite status. His efficiency also helps his chances of winning games.

SP Logan Gilbert

2024 Seattle Mariners Pitching Preview (3)

In 2021, Seattle pushed Gilbert to the majors after one start at AAA (one run over five innings with no walks and five strikeouts). Over his first 11 starts with the Mariners, he went 4-2 with a 3.50 ERA, 0.982 WHIP, and 62 strikeouts over 54 innings. His arm went backward over his next seven starts (8.72 ERA, .321 BAA, and eight home runs over 32 innings). In September, Gilbert threw the ball well over 33.1 innings (2.70 ERA, 1.020 WHIP, and 31 strikeouts).

He gave fantasy teams an excellent first 21 starts in 2022 (10-4 with a 2.78 ERA, 1.146 WHIP, .234 BAA, and 118 strikeouts over 123 innings). The Yankees drilled him in his subsequent two appearances (13 runs, 22 baserunners, and four home runs over 9.1 innings). Gilbert pitched at a high level again over his final nine games (2.53 ERA, 1.050 WHIP, and 52 strikeouts over 53.1 innings).

From a distance, Gilbert had an underachieving feel last year, but his WHIP (1.075) finished in an excellent area while not matching up with his ERA (3.73) due to an increased number of home runs allowed (1.4 per nine). His ERA ranged from 3.56 to 4.38 from April 26th to the end of the season while having a 14-start stretch with a 2.87 ERA and 81 strikeouts over 87.2 innings. He allowed three runs or fewer in 24 of his 32 starts.

His average fastball (95.8) had plus velocity, but batters hit 14 of their 29 home runs off his four-seamer (.281 BAA). Gilbert flashed a winning slider (.210 BAA) with growth with his curveball (.211 BAA). He dumped his changeup in favor of his split-finger fastball (.169 BAA)

Fantasy Outlook: Gilbert finished with an elite walk rate (1.7), but he only had a slight gain in his strikeout rate (8.9 – 8.4 in 2022). His secondary pitches have elite success, and the addition of the split-finger pitch should lead to more strikeouts this year. His ADP (66) in the high-stakes ranks him as the 19th starting pitcher off the table. His FPGscore (3.46) was the 16th-best outcome last season for a starter. Gilbert doesn’t have the sexiness of George Kirby, but he checks the command box with an elite fastball and winning secondary pitches. Next step: 15 wins with 200+ strikeouts and plenty of help in ERA and WHIP.

SP Bryce Miller

2024 Seattle Mariners Pitching Preview (4)

After underperforming in his college career (8-6 with a 4.07 ERA and 141 strikeouts over 110.2 innings), the Mariners drafted Miller in the fourth round in the 2021 MLB June Amateur Draft. His arm shined in 2022 over three levels of the minors (7-4 with a 3.16 ERA and 163 strikeouts over 133.2 innings).

Last year, Miller had four starts at AA with a sharp decline in value (14 runs, 26 baserunners, and five home runs over 19.2 innings). Surprisingly, his arm was major league-ready. He dominated over his first five starts (1.15 ERA, 0.510 WHIP, and 28 strikeouts over 31.1 innings), but the league caught up to Miller in his next two starts (15 runs, 20 baserunners, and three home runs over seven innings). Over his final 18 starts, he posted a 4.26 ERA and 86 strikeouts over 93.0 innings due to surrendering 15 home runs and five disaster outings (27 runs, 41 baserunners, and 10 home runs over 24.2 innings).

Miller had massive struggles against lefties (.303 with 12 home runs over 231 at-bats). His average fastball came in at 95.1 mph with a high usage rate (58.4). Batters hit .254 vs. his four-seamer while earning an edge with his cutter (.196 BAA) and low-volume changeup (.167 BAA). He struggled with his slider (.300 BAA).

Fantasy Outlook: His scouting report paints an electric fantasy fastball with life in the strike zone. His command has improved in the pros, and his cutter is a new pitch. His ADP (187) falls in an upside area of drafts. Miller has plenty of work to do vs. lefties, inviting some down days. I expect him to dominate against right-handed batters. An interesting arm and one I’ll pay attention to this spring to see if his shortfalls are now assets.

SP Bryce Woo

2024 Seattle Mariners Pitching Preview (5)

Woo started his 2023 season with Bryce Miller at AA, but he needed nine starts (3-2 with 2.05 ERA and 59 strikeouts over 44.0 innings) before earning his chance in the majors.

Seattle drafted him in the sixth round of the 2021 MLB June Amateur Draft. Over three years in college, Woo struggled in the bullpen and starting (4-7 with a 6.36 ERA and 89 strikeouts over 69.1 innings). TJ surgery cost him some development time.

After a rough major league debut (six runs and eight baserunners over two innings with four strikeouts), he gave the Mariners six winning starts (2.20 ERA and 39 strikeouts over 32.2 innings). Woo was up and down over his final 53.0 innings (4.58 ERA and 50 strikeouts).

His average fastball (95.2) was challenging to hit (.206 BAA), as well as his sinker (.211 BAA). Woo battled his cutter (.261 BAA) and slider (.257 BAA) with a losing show-me changeup (.400 BAA). His secondary pitches had less value against lefties (.283 with nine home runs, 23 walks, and 35 strikes over 152 at-bats – all pitches combined).

Fantasy Outlook: Woo has pieces to the winning puzzle but feels like a one-trick pony with good command. A year in the majors should help his development and give him some thoughts on what to work on over the winter. His ADP (186) is in a tight range with Bryce Miller as drafter's coin flip on who has the better path to success in 2024. The good days should outweigh the down starts, pointing to a helpful arm with value in strikeouts.

SP Emerson Hanco*ck

2024 Seattle Mariners Pitching Preview (6)

Hanco*ck ended last year with a right shoulder injury that should be cleared up before spring training. Seattle drafted him sixth overall in the 2020 MLB June Amateur Draft. He went 16-7 with a 3.47 ERA and 206 strikeouts over 192.0 innings.

After success over two minor league levels in 2021 (2.62 ERA and 43 strikeouts over 44.2 innings), Hanco*ck had to repeat two seasons at AA (4.42 ERA and 204 strikeouts over 199.1 innings).

The Mariners gave him three starts last year (4.50 ERA, 1.333 WHIP, and six strikeouts over 12.0 innings). His average fastball (92.9) came in below the league average while working off a changeup and cutter as his secondary pitches.

Fantasy Outlook: Hanco*ck gains plusses for his pitch ability while his command is trailing some of the better arms in the Mariners’ system, two of which made the majors last year with success. He has yet to solve AA, and his shoulder issue is a concern. His next step should be AAA, where time in the bullpen may lead to a better path to success.


CL Andres Munoz

2024 Seattle Mariners Pitching Preview (7)

Over five seasons in the minors, Munoz went 9-6 with a 3.12 ERA and 160 strikeouts over 112.2 innings while converting 15 saves. In his minor league career, he struggled with walks (5.4 per nine).

The Padres called him up to the majors in mid-July in 2019, which led to an outstanding 21.1 innings to start his career (1.69 ERA and 27 strikeouts). Unfortunately, Munoz blew out his right elbow in March of 2020, leading to TJ surgery. In 2021, he made five appearances between the minors and the majors (two runs, four baserunners, and eight strikeouts over 41. Innings).

In 2022, Munoz teased closing upside in April (two runs, seven baserunners, 14 strikeouts, and one save over seven innings), but he lost his way over his next 15 games (10 runs, 21 baserunners, and four home runs over 13.1 innings with 11 strikeouts). From the middle of June to the end of the season, Munoz had only two shaky appearances (five runs and five baserunners over two innings) over his 42 games, leading to a 1.67 ERA, 0.672 WHIP, .141 BAA, and 71 strikeouts over 44.2 innings) while securing only three saves. After the season, Munoz had surgery on his right foot. The Mariners expect him to be ready for the start of the season.

Four appearances (no runs over 3.1 innings with three strikeouts and a save) into last season, Munoz landed on the injured list for two months with a right shoulder issue. Seattle used him in a setup role through the end of July (3.38 ERA and 31 strikeouts over 21.1 innings ~ one disaster game included – four runs and four hits over one inning). After trading away Paul Sewald, the Mariners gave him the bulk of saves for the remainder of the year (11-for-13 with a 2.96 ERA and 33 strikeouts over 24.1 innings).

His average fastball (99.1) is one of the best in the game while featuring a dominating slider (.230 – .131 BAA in 2022) that he used less in 2023 (48.6% usage – 64.5% in 2022). Munoz added a sinker (.229 BAA) last year while improving the value of his four-seamer (.184 BAA).

Fantasy Outlook: Over the past two seasons, Munoz teased that he was the next big thing in the closing market. His command was much better in 2022 (2.1 walks per nine – 4.0 last year), making him easier to hit (.217 – .189 in 2022). Injuries have held him back in his career. His ADP (89) in the NFBC puts Munoz in the bet on the come category for saves. Even with 13 saves in 2023, he ranked 108th for pitchers by FPGscore (-3.22). I don’t think he is a slam dunk to get all the saves in Seattle, with Matt Brash being two command ticks away from a beast arm. Possible 40+ saves with over 100 strikeouts.

RP Matt Brash

2024 Seattle Mariners Pitching Preview (8)

After pitching well over three seasons in college (12-7 with a 2.97 ERA and 215 strikeouts over 190.2 innings), the Padres selected Brash in the fourth round of the 2019 MLB June Amateur Draft. The Mariners acquired him in the summer of 2020 for SP Taylor Williams.

In his first entire season in the minors in 2021, Brash went 6-4 between High A and AA with a 2.31 ERA and 142 strikeouts over 97.1 innings. His walk rate (4.4) needed plenty of work while posting an elite strikeout rate (13.1).

In 2022, Brash pitched his way onto the Mariners’ starting rotation out of spring training. His lack of command (17 walks over 20 innings) led to a 7.65 ERA and 19 strikeouts and a trip back to AAA (3.46 ERA and 41 strikeouts over 26 innings). When he returned to the majors, Seattle pitched him out of the bullpen (2.35 ERA, .202 BAA, and 43 strikeouts over 30.2 innings). Brash walked 5.9 batters per nine innings in the majors.

Seattle used him as high volume (78 appearances – most in the American League) last year. He lowered his walk rate (3.7), leading to a jump in strikeouts (13.6 per nine). Despite his growth season, Brash still left a dent in a fantasy team’s WHIP (1.330). After a slow start over his first 24.0 innings (4.88 ERA, 1.625 WHIP, and .290 BAA), his arm reached a much higher level (2.12 ERA, 1.187 WHIP, .213 BAA, and 61 strikeouts over 46.2 innings).

His average fastball (98.2) was electric while offering a swing-and-miss slider – .167 BAA with 76 strikeouts over 162 at-bats ~ 55.5% usage). Despite plus velocity, his four-seamer (.338 BAA) wasn’t an edge pitch. The move to the bullpen led to fewer curveballs (.286 BAA – .235 vs. lefties).

Fantasy Outlook: Brash must solve left-handed batters (.281 with 15 walks and 36 strikeouts over 121 at-bats) before being trusted as lead closing arm. His pitches have plenty of life and movement, and his command is improving. He must locate his fastball better in the strike zone. His ADP (248) seems high for an arm that doesn’t project to earn many saves. On the positive side, Brash can pitch multiple innings, and his strikeout ability plays up as a third starting relieving option on a fantasy team. He comes off the board as the 99th pitcher this year while ranking 82nd by FPGscore (-2.27) for pitchers in 2023. With 15 combined wins and saves with 100+ strikeouts, Brash should be well worth the investment while offering home run upside if earning more saves.

RP Gregory Santos

2024 Seattle Mariners Pitching Preview (9)

Over six seasons in the minors, Santos went 11-16 with a 3.56 ERA and 190 strikeouts over 225.0 innings while splitting time between starting and pitching in the bullpen. He never pitched more than 50.0 innings in any season.

The White Sox gave Santos his first chance at meaningful innings in the majors in 2023, leading to the best season of his career. He solved his command issues (2.3 walks per nine), but batters still hit .258 against him. From April 12th to August 15th, Santos went 2-0 with a 2.19 ERA, 1.125 WHIP, .238 BAA, and 53 strikeouts while converting four of five saves. Over his final 10 games, he allowed nine runs and 17 baserunners over 9.1 innings. His season ended with a right elbow injury.

His average fastball (98.8) had an edge in velocity but not success (four-seamer – .308 BAA and sinker – .340 BAA). Santos threw his slider (.192 BAA) as his top pitch. Righties hit .269 against him with some command issues (11 of his 17 walks over 149 at-bats).

Fantasy Outlook: The questions with Santos's right elbow give him a wide range of draft value in the fantasy market. His ADP (398 - expected to fall dramatically after the trade) in the early draft season has a low of 216 and a high of 469 in mid-January. With a minor league resume full of questionable command, he has an equal chance of regressing as improving this year. His elbow injury could be season-ending before the lights go on in 2024. On the positive side, his price point removes a lot of risk.

RP Ty Adco*ck

2024 Seattle Mariners Pitching Preview (10)

The Mariners drafted Adco*ck in the eighth round of the 2019 MLB June Amateur Draft after two seasons at Elon University (4-1 with a 3.80 ERA and 48 strikeouts over 42.2 innings). After not pitching in 2020 (no minor league baseball), he blew out his right elbow the following April (TJ surgery), knocking him off the prospect lists for 18 months.

Last year, Adco*ck pitched well over 19 appearances between High A and AA (1.74 ERA and 22 strikeouts over 20.2 innings). Seattle called him up in mid-June, where his arm looked sharp over nine games (no runs, four hits, no walks, and seven strikeouts over 12.0 innings). He lost his confidence over his following three outings (seven runs, seven hits, and four home runs over 3.2 innings), leading to a trip back to the minors. The Mariners placed him on the injured list (undisclosed) after one more appearance at AA.

His average fastball (96.5) graded well (four-seamer – .148 BAA) while offering a winning slider (.226 BAA).

Fantasy Outlook: With a minimal resume and no news on his late 2023 injury, Adco*ck is only a follow in the fantasy market until he adds more length to his innings at any level in pro ball.

2024 Seattle Mariners Pitching Preview (2024)
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