Bryce Miller's fastball is coming. It's coming right down Broadway. And you still can't hit it.

Forget keeping hitters off-balance. Miller has overpowered nearly every batter he's faced in his first four big league outings. The Mariners' 24-year-old rookie right-hander has allowed only 13 baserunners in 25 1/3 innings, tied for the fewest ever for a pitcher with at least 20 innings pitched through his first four career starts. He has a minuscule 0.513 WHIP.

Over 70% of the batters Miller has retired have gone down via the fastball. So in start No. 5 against the A's on Wednesday, look for more heat.

"Right now, it's just kind of 'Prove that they can hit it' before I stray away from it," Miller told MLB.com's Daniel Kramer.

Miller is throwing the most four-seam fastballs of any starter in baseball right now. He is the only starter throwing his fastball over two-thirds of the time.

SP with highest 4-seam fastball usage in 2023

1. Bryce Miller: 67.7%
2. Michael Kopech: 63.3%
3. MacKenzie Gore: 62.1%
4. Spencer Strider: 61.3%
5. Justin Steele: 60.9%

Miller throws over four fastballs for every one slider, and over six fastballs for every curve, and nearly 14 fastballs for every changeup. His fastball is his most-used pitch in every count, usually by far. But hitters are still batting just .117 against Miller's four-seamer, with seven hits in 60 at-bats.

"I think the thing that we've done pretty well with our young guys is, we go with what's working," manager Scott Servais said. "We're not going to try to invent stuff on the fly. Even though he's got good secondary pitches, if he's getting them out, we're going to stick with that."

The reason Miller can keep beating hitters by throwing fastball after fastball is because he already has one of the most explosive rising heaters in the Majors.

Miller averages 95.3 mph on his four-seamer with an elite 2,605 rpm spin rate, the highest among starting pitchers. That top-tier spin produces top-tier "rise" -- it makes the fastball look like it's rising to a hitter, because it drops less than the hitter expects, which makes it harder to connect.

Miller's fastball generates 3.3 inches more rise than an average four-seamer. That ranks No. 1 for MLB starters this season.

SP with most fastball "rise" in 2023

1. Bryce Miller: +3.3 inches vs. avg.
2. Nestor Cortes: +3.2 inches vs. avg.
3. Spencer Strider: +3.0 inches vs. avg.
4. Taj Bradley: +2.9 inches vs. avg.
5. Tyler Mahle: +2.8 inches vs. avg.

Rise vs. avg.: Compared to 4-seamers thrown with similar velo + release point

Miller has some Spencer Strider in him. Strider's old-school power fastball -- and his willingness to attack hitters relentlessly with it -- fueled his breakout with the Braves a season ago.

Miller pitches with the same aggressiveness. And his fastball is like Strider's, too -- a high-velocity rising fastball that can dominate hitters all by itself.

Miller can blow his fastball by you upstairs in the prototypical way -- a high-spin, rising fastball can be lethal at the top of the zone -- but he can also pound the strike zone with it, and rely on its carry through the zone to make it explode on a hitter before he can do anything with it.

"The fastball up is always there, but definitely whenever I can command both sides of the plate, it makes things a lot tougher on them," Miller said. "We're definitely in on not only going fastball up the whole time -- going in, out, down, up, that definitely helps."

Look at the heatmap of Miller's four-seamer. He is not just elevating it. He is also filling up the strike zone with it.

Miller has been fearless:

• 55.7% of his pitches this season have been in the strike zone, top five among starting pitchers -- and right behind Strider (56.6%)
• 36.3% of his pitches this season have been in the heart of the strike zone -- that means more than a baseball's width inside the edges of the zone -- the highest rate among starters, just ahead of teammate George Kirby
• 11.4% of his pitches have been perfectly middle-middle in the strike zone, also the highest rate among starters

That's how you get a 2.3% walk rate that's the second lowest among all starters (only Kirby walks fewer hitters), and Miller's fastball is so good that he has a 25.0% strikeout rate to go with it (his four-seamer has produced 18 of his 22 K's).

The only starting pitcher with a better strikeout-to-walk ratio than Miller's 11.0 is Jacob deGrom. Miller challenges every hitter, and he usually wins.

He has been one of the best pitchers at suppressing offense in the heart of the zone, where you might expect hitters to be able to do the most damage. Based on the result of every pitch he's thrown in that region, Miller has been worth nine runs prevented for the Mariners in the heart of the zone alone -- easily the best of any pitcher since he made his debut.

"Our mentality, really in all accounts, is early in counts, get ahead, throw strikes," Miller said. "I'm fine with my stuff being [good enough that] if I miss middle, then I miss middle. They've still got to hit it, so I'm not worried about going in [at hitters]."

MLB.com Mariners beat reporter Daniel Kramer contributed reporting to this story.