Looking at Mason Miller's Debut
Miller was unknown to most baseball fans a month ago. Now he's the A's one bright spot on the mound. How did he do on MLB debut after just 30 innings of professional baseball?
Oakland prospect Mason Miller made his highly anticipated debut on Wednesday against the Cubs, which was a welcome surprise given he has only thrown 28.2 innings in the minor leagues ever. He was drafted at age 22 in 2021, which explains why he’s further along in development than most pitching prospects. But his 53:6 K:BB ratio in those 28+ innings, including a literally perfect 5-inning, 11-strikeout outing with just 65 pitches against the AAA Salt Lake Bees on April 14th, remains extremely impressive. It’s clear that he has superstar potential.
His First Start
His line wasn’t too impressive vs. the Cubs at home, going for 4.1 innings, 4 H, 2 ER, 1 BB, 1 HBP, 5 Ks in 81 pitches. His CSW% was a mediocre 27% on account of his weak command, while his SwStr% was a solid 12%. His fastball averaged 99 mph, as one hoped, and topped out at 102. He seemed to aim for up in the zone with it, in conjunction with his 93(?) mph slider down. In practice, his slider location was extremely inconsistent - sometimes middle middle, sometimes pretty well placed down and away - leaving his fastball to do much of the heavy lifting. His cutter was worked in 11 times as well with an excellent 36% CSW. It’s clear that he has the raw stuff to be an above-average big-league starter already, but he needs some refinement to reach his potential. The Las Vegas A’s aren’t complaining, though; they’re starting Shintaro “14.40 ERA 2.07 WHIP 12 K:12 BB” Fujinami otherwise. Weird nickname.
A plot that’s a little over the place on debut, but shows clear intent. [BaseballSavant]
Pitch Mix
Fastball - He throws it 99 mph. What else can one say? He’s currently 1st on FanGraphs amongst all pitchers in that category amongst all listed starters. Still, he’ll probably drop into the mid-98 mph range that Jacob deGrom (98.6) and Hunter Greene (98.4) currently reside in. It wouldn’t be the first time someone threw 1-2 mph harder on avg during their debut. It packs an induced vertical break (IVB) of 18.2 in. with a VAA of +.19॰, both well above average and plays into his fastball-up approach. The pitch will be able to overpower hitters as long as it’s remotely well-placed. I’m not too concerned about this one.
Slider - His go-to secondary, his slider was used 22% of the time on his debut. Thrown at 86.8 mph, it has 9.1 in. of horizontal break. That means he has a difference of 17 in. worth of horizontal movement between his fastball and slider, which is too much for ideal tunneling. He uses it primarily against right-handed hitters, and as long as that horizontal separation doesn’t cost him, looks fine.
Cutter - Thrown at an electric 95.4 mph, it’s the perfect bridge pitch between his fastball and slider. Advanced stats that I’ve seen hate it so far, but he only threw it 11 times on debut, and he had solid command with it. I think for him to find success long-term, the cutter will have to find its mark - it’s his go-to secondary vs. lefties. I think it’d be sufficient if he could throw it 20-30% of the time against LHP with confidence (he threw it 22% of the time to them on debut).
Changeup - He only threw it once, so there is not much to say about it. It clocks in at 92.3 mph and looks like a solid offering. Maybe he’ll grow into it with time; I think Miller could one day use this pitch 10-15% of the time at the minimum as another tool for lefties.
Unfortunately, PitcherList doesn’t have Miller in their database yet, so I can’t use one of their beautiful pitch movement graphics yet. [Data and color scheme from Alex Chamberlain’s Pitch Leaderboard]
A Relevant Comparison
The best comparison to Miller I can think of is Spencer Strider. It’s a common one but an apt one. They’re both flamethrowing fastball/slider pitchers that may have trouble going deep into games. Here’s how they compare:
Fastball: Miller throws it 2 mph harder, giving it a comparable spin rate despite being less efficient. Also, they have a VAA gap of +.2॰, which is relatively significant. I’d wager Strider’s fastball performs a little better.
Slider: Also thrown 2 mph harder. Miller gets 4 more inches of horizontal break on his slider, which makes it tunnel worse with his fastball than Strider, who has a perfect 12-13 in of difference between them. Again, Strider’s gets a slight edge here.
Cutter: Strider doesn’t have one. He opts for a changeup at ~5% usage instead.
Changeup: In terms of velocity, Miller throws his 4 mph harder than Strider does. That’s a huge difference. Miller also opts for 2 two less in. of IVB for 2 more in. of HB, which actually creates the exact same observed drop between the two because of how much harder Miller throws it. Miller’s changeup seems to be clearly better, especially because he maintains a solid speed differential with his fastball on it despite being thrown 92 mph. That’s as fast as many people’s fastballs.
Overall: Despite the better velocity across the board, I’m not sure he’ll mirror Strider’s rapid rise. His fastball/slider separation is worse, and his command will likely be worse as well; Strider’s BB rate was a reasonable 8% last year. I envision the next step in Miller’s game coming from the development of his cutter or changeup into a trustworthy pitch to get lefties out or sufficient command to achieve fastballs up/breaking balls down truly.
Conclusion
I’ve seen many people reference his elite Stuff+, and it’s certainly nothing to sneeze at. A 133 is 3rd-best in baseball, only behind Ohtani and deGrom. One has to be careful though: Ashcraft and May join him in the top 10, while Cole is 12th, and McClanahan, who just got 32 whiffs on 87 pitches, is 16th. It’s early, and it’s promising, but command and sample size matters too.
My fairly aggressive prediction: 5.5 IP/Start, 3.3 ERA, 1.1 WHIP, 30% K, 10% BB (virtually 2022 Dylan Cease, but with a far worse ERA). I think he’s a more volatile version of Strider with the lack of professional innings, but the stuff will get him across the line. I don’t think he’ll have the horrendous command of Cease’s early years because he never had lousy command in the minors, and a 10% walk rate might even be a bit much. I’m excited to see how his second start goes; I want him to dominate and prove me completely wrong.
Sources:
PitcherList
FanGraphs
Alex Chamberlain's Pitch Leaderboard v5
BaseballSavant