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The best (and worst) four-seam fastballs on the 2019 Mariners

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The fun thing about superlatives is they exist no matter what.

Seattle Mariners v Pittsburgh Pirates Photo by Justin Berl/Getty Images

What do you like in a fastball? Soaring velocity? Bat-shattering run? Worm-burning late sink? Whatever Nick Vincent does? The 2019 Mariners had few of those things, leading some writers to claim they should abandon their tepid heaters entirely. To their credit, Seattle was aggressive in taking their foot off the gas. Still, staffed with mostly soft-tossers and unproven relievers, the Mariners were far from the forefront of the high-spin, high velocity, up-in-the-zone four-seam trend that aces like Gerrit Cole, Justin Verlander, and Tyler Glasnow have put front and center. What did the Mariners get out of their heaters this past year, then? Not much.


You don’t need advanced metrics to know Seattle’s pitching staff wasn’t great last year. If you watched many of the Mariners games last year, you were unlikely to be treated to something resembling most of the modern sport. Below is a chart of four-seam fastball velocity from 2019, split by team. Seattle ranks dead last.

Four-seam fastball data from Baseball Savant

Baseball Savant’s numbers stretch back to 2008, showing the last time Seattle’s 2019 average four-seam heat of 92.2 mph would have been above-average was 2010, when the league average rate was 92.1. Last year, MLB’s average four-seamer was 93.4 mph, and while velocity isn’t everything, it’s the most easily measured benchmark for how much success hitters will have against a heater. Hitters, quite clearly, had a grand old time against the Mariners and their four-seamers.

Mariners 2019 Four-Seam Fastballs

Pitch # of 4FB Thrown % of Total Pitches = 4FB wOBA (Rank) wFB wFB/C
Pitch # of 4FB Thrown % of Total Pitches = 4FB wOBA (Rank) wFB wFB/C
Four-Seam FB 6078 (30th) 25.3% (30th) .405 (30th) -87.2 (28th) -0.79 (28th)
Data by Baseball Savant and FanGraphs

It’d be remarkable if it weren’t so brutal. wFB (weighted Fastball) and wFB/C, for anyone unfamiliar, are Pitch Value metrics from FanGraphs, which, from their explainer, “attempt to answer the question, ‘How well has a batter/pitcher performed against/using a certain pitch?’” I recommend reading over the linked explainer, it’s fairly intuitive, but the long and short is...

1. Pitch Values like w/FB are estimating the runs allowed above or below average (which is 0.0) of a pitch,
2. wFB/C standardizes the total on a per-100 pitches basis, to offer a rate stat (in other words, it’s like total strikeouts vs. K/9), and,
3. The results of a pitch only tell us so much about its quality. A good fastball is more effective when a pitcher also has a good changeup or breaking ball to keep the hitter guessing. Conversely, a fastball that should be good in a vacuum is liable to underperform if hitters know that’s the only thing that’s coming.

By these metrics, the Orioles and Rockies had worse four-seams than Seattle, but considering the M’s threw four-seamers significantly less frequently than the rest of the league, their numbers belong closer to the bottom step of the basement stairs than they were to the ground floor.

Not everyone was a disaster, though.

Sit your ass down Mr. Seeds
MLB/Baseball Savant

If you checked out of the final couple months of 2019, you might be hard-pressed to name who served as Seattle’s closer by season’s end. Matt Magill, shown above in MLB’s disastrous “Players’ Weekend” threads, had what I am inclined to name the Mariners’ best four-seam fastball last year.

Seattle snagged Magill from the Twins last July, offering Minnesota cash to jump the line on the waiver wire. In a competitive season, this might’ve been a decisive pickup, as Magill immediately became a reliable high-leverage worker. Instead, Magill’s competence was more like extinguishing a candle while the house burns down around you.

Fortunately, Magill remains a Mariner, and can contribute to rebuilding both the metaphorical house and the actual Mariners roster, and to do so he’ll need to keep his fastball sharp. Magill averaged just over 95 mph on his four-seamer last year, and upon joining the Mariners he threw the pitch 56.9% of the time. While he throws both a slider and a curveball, Seattle encouraged him to amp up his fastball rate, and focus on his curve. With a curve that delivers near 12-6 movement at excellent velocity, his fastball seems to pop all the more.

Using Jake Mailhot’s Stuff+ metric, which attempts to combine velocity, movement, command, and spin rate for a standardized grade a la wRC+/OPS+/ERA+ (100 = league-average, every point higher or lower is a percentage better or worse than league-average), we can see Magill is near the top of the Mariners’ four-seam leaderboard.

Mariners 2019 Four-Seam Fastballs Stuff+

Player Stuff+ Total Four-Seams Thrown Avg. Velocity Whiff Rate
Player Stuff+ Total Four-Seams Thrown Avg. Velocity Whiff Rate
Gerson Bautista 166 124 97.7 16.39%
Dan Altavilla 166 166 96.6 17.07%
Matt Magill 143 451 95.2 27.27%
Connor Sadzeck 136 160 96.4 30.00%
Erik Swanson 120 657 92.7 27.27%
Austin Adams 103 174 95.1 23.44%
Matt Wisler 100 81 92.9 12.90%
Justin Dunn 90 77 92.5 9.09%
Sam Tuivailala 86 130 93.5 29.79%
Mike Wright 84 199 93.3 23.91%
Yusei Kikuchi 81 1287 92.5 16.00%
Matt Festa 80 176 92.6 16.67%
Justus Sheffield 73 322 92.8 12.78%
Zac Grotz 57 108 92.2 11.63%
Tommy Milone 52 730 87.1 10.99%
Wade LeBlanc 50 111 86.3 16.13%
Felix Hernandez 46 91 89.9 17.24%
Chasen Bradford 29 86 90.6 23.26%
Min. 75 four-seam fastballs thrown Jake Mailhot

Few Mariners threw four-seamers with great regularity, and even Magill’s numbers above include his time with the Twins, but his effectiveness only grew in Seattle, and makes me inclined to name his fastball the club’s reigning champ. Still, two players are listed above him by Stuff+, and both suffer similar issues. The first is Gerson Bautista, who had Seattle’s firmest fastball, and could overpower hitters like this:

Baseball Savant

But a number of factors undermined Bautista’s effectiveness overall. For one, while his command and Magill’s were not so drastically different on paper, Bautista’s fastball got absolutely clobbered in his time in Seattle. Much of that appeared to come down to three characteristics - how his fastball moves, where the fastballs were located, and how good his off-speed was.

For Bautista, unfortunately, his fastball rarely landed as near to the glove as the gif above. Despite a trebuchet-esque delivery that releases the ball nearly directly down the middle of the rubber, Bautista often left the ball in the lower third of the zone. Bautista’s over-the-top release encourages backspin, which plays far better at the top of the zone, and yet...

Gerson Bautista Four-Seam locations
Baseball Savant

Not ideal. While Bautista’s fastball has impressive carry and does not sink much during its flight, it has almost no horizontal movement (just 3.3 inches), meaning it flies like a crossbow bolt towards the heart of the plate. Too often, the barrel of an opponent’s bat is waiting.

Baseball Savant

Bautista used a slider that was underwhelming in 2019, but had arrived in spring training showing a more promising offering. Some combination of an improved breaking ball and better locations on his fastball could help him, but for now, Magill gets a greater vote of confidence.

Much like Bautista, Dan Altavilla has many the traits of a great power reliever, but hasn’t been able to deliver consistently. Injuries and inconsistency impacted Altavilla last year, but his heater has significant arm-side run in addition to solid carry and velocity. Skyrocketing walk rates have been the main foible for Alt, as well as a deeply inconsistent off-speed repertoire that has helped hitters sit on his heat.

While Bautista, Altavilla, and Magill are the only pitchers with a particularly strong case for the best four-seamer on the team, there’s any number of options for last place. Chasen Bradford earned the worst Stuff+ rating on the club, but with only 86 four-seamers prior to season-ending injury, it’s not particularly sporting to harp on him further. King Félix looked pauper-ish as well, but he was clearly cognizant, using the 89.9 mph pitch just 7.5% of the time in his final season in Seattle. Yusei Kikuchi threw nearly two times the four-seamers of any of his teammates, with below-average results, but his issue appeared to be one of inconsistency over true mediocrity. While Kikuchi did have far too many pitches that looked like this...

Baseball Savant

...there was enough of this to at least hint at something better.


Despite his subpar debut season, the metrics on Kikuchi’s fastball at least showed features of above-average heat at times. The same cannot be said for some of his former teammates.

After considering the options, I’m laying this dubious laurel wreath on the head of one Tommy Milone. This is, quite simply, neither a competitive pitch, nor a modern fastball.

Baseball Savant

As a one-time soft-tossing, command-focused pitcher myself, this is not a diatribe against Milone for something out of his control. Milone has never thrown hard, yet he’s carved out nine years of a big league career, and will likely make some appearances with his new club, the Orioles, if and when a season comes together this summer. Hell, he didn’t have a terrible season in 2020, as his 4.76 ERA helped him to 1.5 bWAR in 111.2 IP, which was good for 7th-best on the team and 3rd-best among pitchers.

No, Milone is on this list because his 2019 season was a case study for the continued decentralization of the fastball as a pitch. It’s not that Milone’s fastball was so slow, though it is, nabbing the 1st percentile in league velocity without a single pitch over 89 mph. It’s that in the face of overwhelming evidence that the pitch was ab-so-lutely not working: a .298 batting average against, a .702 slugging against, and a wOBA/xwOBA of .428/.382, Milone solemnly nodded when a single finger was held down 43.7% of the time, a plurality among his pitches only remotely approached by his changeup (38.1%). While Milone’s changeup was actually a fairly effective pitch, and by its nature somewhat dependent on the existence of a fastball for counterweight, nothing in Milone’s fastball’s suggests it is providing enough cover for the rest of his repertoire.

At times, that’s given the illusion of an entire play in slow motion, including but not limited to: his motion, the ball, the batter’s swing, the crowd’s reaction; everything but Keon Broxton’s futile pursuit seems to move as though the temperature is nearing absolute zero.


Yet the result, too often, was the same. Slow-mo fastball, slow-mo swing, slow-mo arc, fast-mo 4-0 deficit. The Mariners have consistently had among the least imposing fastballs in the league over the past few years, but they’ve found gems at times. Nick Vincent thrived with a 90-scraping four-seamer. Wade LeBlanc whipped up his own brand of even year magic in 2016 and 2018. Joel Peralta struck out Mike Trout that one time. Even Milone wasn’t a disaster on the whole, racking up 1.5 bWAR on his 4.76 ERA despite a 5.00 FIP and 0.1 fWAR. But the tightrope walk required to succeed with that lack of velocity isn’t one many players or teams can balance forever. Seattle’s ever-swelling stable of young starters with above-average velocity suggests they intend to change up the show soon.