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Andrés Muñoz: the 2022 Mariners Closer (maybe? We hope)

don’t pin your dreams on bullpen arms but when they look like this it’s hard not to

San Diego Padres v San Francisco Giants Photo by Ezra Shaw/Getty Images

When recording the Lookout Landing podcast the other day, Joe Doyle casually dropped a hot take, suggesting that Andres Munoz, not Taylor Trammell, could be the headliner of that trade. It’s easy to see why. Muñoz is the lucky owner of a very special arm, one that can easily deliver triple-digit heat—a true 80-grade pitch. The Padres signed Muñoz out of Mexico in 2015, with a relatively sizable signing bonus of $800K, as he was already a) pitching professionally for the Mexico City Reds and b) comfortably in the mid-to-upper-90s and occasionally touching triple digits as a 17-year-old. After a relatively quick ascent through the minors due to his professional track record—he was the youngest player at the Arizona Fall League in 2017, just 18 years old—Muñoz made his MLB debut in 2019, striking out 30 batters in just 23 innings of work with the one-two punch of his triple-digit fastball (it averaged, averaged 99.9 mph) and a nasty slider (86.5 mph).

If your mental rolodex for “flamethrowing reliever with a plus slider” immediately dials up Edwin Diaz, be aware the two physically look very different. Whereas Díaz was long and lithe, a tensile wire shot through with electricity, Muñoz, only an inch shorter, somehow seems much stockier, with a thick lower half and broader chest.

MLB: San Diego Padres at San Francisco Giants Darren Yamashita-USA TODAY Sports

Where Díaz and Muñoz are similar is in the electric whip of their arms producing easy velocity. With Muñoz’s more powerful frame, however, that pushes his velo from the high 90s to well over triple digits.


The Padres, to their credit, leaned heavily on Muñoz to develop his slider and not just rely on mowing minor-leaguers over with his fireball. He even had rules for when he had to throw his slider in counts to batters. In his 23 MLB innings, Muñoz threw the fastball about two-thirds of the time compared to just one-third for the slider, but it was the slider that did the damage; batters hit just .065 on it (and an xBA of .074 suggests that wasn’t a fluke), and he got lots of whiffs on the slider—46.3%, vs. 22.6% on the fastball. Since sliders are whiffed on so much more often than fastballs, it’s useful to contextualize those numbers. Muñoz’s fastball whiff/swing rate of just over 22% was fine, but placed him in the back half of the top 200 relievers (165); his slider whiff rate placed him just outside of the top 30 for whiff/swing rate among all relievers in 2019 (and just a tick ahead of Austin Adams, for whom he was traded).

As it is for Díaz (sad moment of silence), the slider is the pitch that makes Muñoz more than just a party trick who throws hard. Man cannot live on fireballs (or Fireball) alone. Muñoz opened the at-bat with a fastball more than 75% of the time in 2019, and if he got the strike, would proceed to work in the slider with more frequency before putting the batter away. However, if he fell behind he had to keep throwing the fastball, which Muñoz can have real issues with reining in, missing horizontally in the zone much more often than vertically, much to the quivering of several abdominal regions around the league, I’m sure.

Muñoz’s issue, as you might have grokked by now, is command. His minor league career numbers follow the traditional roller-coaster trajectory of a young prospect: his FIP starts high in his debut, then steadily ticks down as he becomes accustomed to pro ball, then rises again as he gets into the upper minors. One thing that has been glumly consistent, however, is his walks. Muñoz’s best BB% numbers are from his 19-inning stint in Triple-A before being summoned to join the big club, and even at that they’re approaching 9%; other than that, they’re solidly in the double digits, and some in the high teens. When watching the pitches he threw in MLB last year it seems to me like Muñoz fell off the mound on the first base side pretty hard when delivering 100 mph+, and not coincidentally a lot of his pitches wound up in the left-handed batters’ box.

When his fastball did land in the zone, it was more hittable than you’d like to see; batters hit .264 off it and slugged .472 on it, but the expected numbers projected an even worse fate of a .294 xBA and a .598 xSLG. Muñoz’s fastball, while in the top .0000001% of the league for velo (I am guessing on that, please do not fact-check me), doesn’t have a lot of other really appealing pitch characteristics. It has average spin and average movement, with 10.1 inches of horizontal break. Compare that to Muñoz’s former bullpen-mate Kirby Yates, who throws significantly less hard but whose fastball gets whiffs almost twice as often as Muñoz’s. Neither have a lot of sink on their fastball, but Yates has about 14 inches of horizontal break on his four-seamer, 60% more than the league average, while Muñoz has around 10, right at league-average. The velocity on Muñoz’s fastball makes it a special pitch, but the other pitch qualities do not, meaning Muñoz is reliant on the interplay between his fastball and slider, with the fastball mostly serving to set up the slider rather than being a fully-realized weapon of its own. So another task for the Mariners’ pitching development will be not only supervising Muñoz’s return to health, and helping him rein in his command, but also maximizing his pitch qualities.

When writing up Taylor Trammell as an acquisition piece, I mentioned that in these profiles I’d be looking to answer four big questions. For Muñoz, the answers are pretty easy:

  • Why did the Padres part with this player? Muñoz had TJ surgery in late March and wouldn’t be able to contribute to a win-now Padres organization until May of 2021, at the earliest. Since he already had been called up, he also requires a roster spot when healthy, although he does have all three of his options remaining.
  • Why did the Mariners target this player? Because the social media team loves using the 100 emoji. And the Mariners have had some degree of success taking fastball-slider pitchers with poor command and helping them fix up that command. In fact, Austin Adams, who was dealt to the Padres in this trade, is a good example of that.
  • What are the risks? Obviously there’s arm health concerns and doctors who will say the human body wasn’t meant to throw 103 mph. I’m not sure it was! The Mariners, like any other red-blooded baseball team in the modern era, do love big velocity, but they love command even more. I wouldn’t be surprised if they had Muñoz back it off a little velocity-wise in order to create better command. Watching how the team progresses with Yohan Ramirez, another fastball-slider flamethrower with abysmal command, might provide a key as to how the team eventually plans to work with Muñoz. (Ramirez, by the way, has a mind-blowing 17.8 inches of break on his slider, 103% more than MLB average. I would not be averse to putting those two together and having them teach each other some things.)
  • Enough about the risks, give me that sweet sweet reward: It’s hard not to get excited when you see the radar gun light up with triple digits. This is elite closer stuff if the command issue can be ironed out and he’s able to stay healthy. Those are two big ifs, but also, bullpen pieces are pretty fungible so I’ll be less disappointed if Muñoz doesn’t grow into Scary Death Closer. With apologies to Joe, to me this is still the Taylor Trammell Trade. T-T-T!

For Muñoz, he won’t be starting from scratch with the Mariners; he was the youngest player on the 2017 Peoria Javelinas in the AFL, a team that included current Mariners Kyle Lewis, Art Warren, and Braden Bishop, among others. The super-team also included Ronald Acuña Jr., Lourdes Gurriel, and Michael Chavis, and they won the 2017 AFL championship (led by league MVP Eric Filia!), so he’ll have plenty of good memories to reminisce on with his new teammates.