In the time you took to open this article, another homer has likely been clubbed off a Mariners pitcher. Don’t put all the blame on them - league-wide the HR/9 has risen to 1.32, the highest in the history of the sport, and only closely matched by 2017 when the baseball’s juiciness came fully into focus. But the Mariners have been among the most heavily impacted teams in the league this year. Only the Orioles, at an astronomical 2.12 HR/9 pace are out-allowing the Mariners at 1.76. Both figures would blaze past the prior record of the 2016 Reds at 1.61, and lead 2019’s third-place White Sox at 1.60 handily.
There are many factors making the dingers and runs allowed balloon, with league-wide ERA and FIP sitting at 4.30, but the decline of the fastball is surely near the top. The value of fastballs has always been nebulous - there’s a reason it’s the pitch nearly every hitter hopes the pitcher is throwing - but in 2019 the heater is in as dire straits as its seen since the steroid era. FanGraphs generates a metric called Pitch Value, designed to judge outcomes based on what is thrown. It’s limited, and of course when pitchers have better secondary pitches their fastballs will play up, but looking league-wide we can see it’s not an isolated issue.
That -223.0 value from fastballs is through 700 games (although it’s 1,400 games for our measurements, looking at both pitching staffs for each game), just under 29% of the season. If we extrapolate that out for the rest of the year at the current pace, we get -774.5 wFB value, the worst since 2006 and third-worst since pitch tracking data has been available for this. But that doesn’t account for usage - fastball use has dropped steadily since 2002. Presumably the rate was even higher at one point, but the rate fell from 64.4% fastballs in 2002 to around 57.7% in 2011, where it plateaued until 2016, then it fell again, now at an all-time low of just 52.8% of pitches thrown.
Moreover, those fastballs are averaging 92.9 mph per FanGraphs and Pitch Info Solutions, almost a full four miles per hour faster than the average heater in 2002.
To recap, then, velocity is up, fastball usage is down, and yet fastball effectiveness is also down. The increased scarcity of the pitch might theoretically make one think it would play up, as hitters look for other pitches more frequently, but that doesn’t yet seem to be happening. To show that another way, we can use Baseball Savant to measure league-wide wOBA (weighted On-Base Average) on fastballs (defined as four-seams, two-seams, and sinkers, but not cutters) each year. It’s currently sitting at .358, which would be the highest mark since 2009 and match the second-highest in Savant’s database, which stretches back to 2008. The 2019 numbers all come just under two months into the season, before the weather has gotten warm in most places and the baseball begins to fly further in the summer heat.
So the rest of the league is suffering, but what of the Mariners specifically? Let’s just say if this is the year the fastball’s fate is sealed, the Mariners may be its executioner. Only the Astros (45.0%) have thrown fewer fastballs per pitch than the Mariners (45.3%) in 2019. Those numbers would be the 2nd and 3rd lowest rates of fastballs EVER, trailing only the 2018 Yankees, yet no team has been more thoroughly decimated when the catcher puts one finger down.
MLB Fastballs thru May 20, 2019
A complete disaster. With the slowest average fastballs in the league it’s not a complete shock that Seattle struggles so, and yet a few other relatively soft-tossing clubs like the Cubs, Padres, and Cleveland have not had nearly the same issues. Seattle seems to recognize its weakness, as they throw their fastballs with relative scarcity, but even the mere plurality of heat that they’re using is clearly far too much - no team is even close to them in negative value, and the gap is even greater in negative value per pitch (wFB/C). If Seattle doesn’t turn things around in a pretty major way, they will easily set the record for worst results on fastballs as a team from the 2005 Royals by rate (-1.07 wFB/C) and the 2002 Devil Rays by total (-161.5 wFB).
Translating that once again to more common metrics, Seattle is allowing a league-worst .419 wOBA on fastballs this year, 25 points worse than the penultimate Rangers. The foremost culprits are Félix Hernández and Mike Leake, each getting absolutely clobbered (unsurprisingly) on their typically <=90 mph heaters, but you likely don’t need me or any advanced metrics to tell you Erik Swanson has seen his high-spin four-seam crushed as well. On the positive end of things, Brandon Brennan and Roenis Elías have put up good results, but it’s a bit early to break down these numbers on an individual level, for relievers doubly so.
There doesn’t appear to be an easy fix to this issue for the Mariners based on their current roster. Mike Leake, Wade LeBlanc, and Marco Gonzales all average <90 mph on their fastballs, and Félix is barely a tick higher. Tonight they’ll start Tommy Milone, who is closer to LeBlanc than Yusei Kikuchi, who is the only M’s starter with non-negative numbers on his fastball (and, unsurprisingly, by far the best velocity). The fastball isn’t a hopeless pitch period - guys like Mike Soroka, Chris Paddack, and Blake Snell have had great success thanks to excellent heaters, and pitchers like last night’s opponent Mike Minor have leaned heavily on theirs for success.
But the Mariners don’t seem to have those types of fastballs, at least not until Justus Sheffield, Justin Dunn, and Logan Gilbert arrive. Even as they mix their pitches more than most of the league, they’d be best served going further down the rabbit hole. They might as well keep digging deeper for more and more junk, because what they’re doing right now isn’t cutting it.