18-Year-Old Miguel Sime’s 101 mph Fastball Blows Off Prospect’s Helmet

This post recaps a standout Spring Breakout performance at Roger Dean Chevrolet Stadium. Eighteen-year-old Miguel Sime Jr. flashed elite velocity and poise against a top pitching prospect.

The breakout put his raw arm strength and late-game feel for pressure on full display. Scouts are already making early reads on Washington’s wave of young arms.

Breakout Night: Sime’s 100+ mph Showdown

In the second inning of the Nationals’ 9-8 loss to the Cardinals, Miguel Sime Jr. made sure people noticed him. The right-hander blistered a 100.8 mph fastball, lighting up the radar guns and grabbing attention from scouts and teammates.

Sime, Washington’s No. 16 prospect, went right at St. Louis’ top prospect JJ Wetherholt in a big spot. He showed the kind of arm strength that makes evaluators sit up and pay attention.

It wasn’t a perfect moment. Sime started the sequence with a pitch-clock violation that threw off his rhythm for a second.

He bounced back, though, and attacked the zone. After falling behind 3-0, he fired two cutters to get chases, then ended the showdown with a full-count, upper-mid-100s fastball.

Out of his 21 pitches that inning, nine hit 100 mph or faster. That’s wild velocity for someone his age.

The Mechanic and the Slider: How Sime Puts Away Bats

Velocity wasn’t the only thing that stood out. Sime mixed his pitches to keep hitters guessing.

Teammates pointed out his imposing presence and the way he stuck to his plan, even when things got tense. He used a gyro slider to set up hitters and complement his fastball.

This helped him get ahead in counts and finish tough at-bats. That combo—a premium fastball and a sharp second pitch—gave him a repeatable look in a showcase setting that can rattle young pitchers.

Despite all that triple-digit heat, Sime insisted he’s happy with his current velocity. “I’m not greedy for more velocity,” he said, sounding pretty grounded for a teenager who’s already on pro radars.

Path, Perspective, and Poise: Sime’s Mindset

Born in Brooklyn and picked in the 2025 draft as a fourth-rounder out of Poly Prep Country Day School, Sime is still just 18. His Spring Breakout outing showed off a mix of raw tools and developing polish.

Scouts see the kind of package that could become a starter who handles late-inning pressure. After the clock misstep, Sime talked about his mindset—he aimed for a first-pitch strike and adjusted on the fly to stay in the contest.

That’s a sign of maturity you don’t always see in someone this young. Several teammates shared their thoughts too, and the praise echoed through the dugout.

“Sime’s velocity and presence are rare at his age,” said Gavin Fien, a fellow prospect watching closely. “You can see the work ethic in his delivery and the way he executes under pressure,” added Eli Willits, pointing out how Sime’s preparation shows up when it matters most.

What This Means for Washington’s Pitching Pipeline

From a scouting and organizational perspective, Sime’s performance checks several critical boxes. He’s a teenager who can throw multiple pitches with plus velocity and still keep his cool in high-stress situations. That’s just not something you see every day in today’s game.

The gyro slider stands out, especially when he pairs it with an elite fastball that’s already touched 100 mph. This combo sketches out a possible future as a high-leverage reliever—or maybe even a starter if he sharpens his command as he matures.

For Washington, the message feels obvious: Sime is a name to watch in this new wave of young arms. The Cardinals game gave everyone a real look at his ceiling and the kind of path he might take as the Nationals try to build up both their bullpen and starting depth over the next few years.

With his current velocity, a refined pitch mix, and the kind of poise you just can’t teach, Sime’s a pretty compelling story to follow for the rest of spring and into minor-league play. I’d keep an eye on him—who knows where this could go?

 
Here is the source article for this story: 101 mph (from an 18-year-old!) blows away MLB’s No. 5 prospect — and his helmet