TRENTON, N.J. -- When Miguel Sime Jr. was just 15 years old, he threw 95 mph off the rubber.
Three years later, that number has climbed into the triple digits -- and the right-hander, now MLB Pipeline's No. 91 Draft prospect, is challenging himself by using that power in the MLB Draft League.
"I just saw it as another opportunity to open some more eyes and show what I've got against better competition," Sime said.
The MLB Draft League, established in 2021, serves as a showcase for top amateur talent ahead of the Draft. The six-team circuit features a mix of Draft-eligible college players and select high school prospects looking to prove themselves and raise their stock.
While many potential early-round high schoolers opt to rest or train ahead of July's Draft, Sime wanted more. He just wrapped up his senior season at Poly Prep in Brooklyn, N.Y., where he posted a 1.16 ERA with 86 strikeouts over 48 1/3 innings. And instead of taking a breather, he's facing off against hitters with far more experience -- some who recently finished their fifth seasons of college ball.
On Wednesday's Opening Night at Trenton Thunder Ballpark, the 18-year-old got the start for the Thunder against a Williamsport Crosscutters lineup with an average age of 22. Matthew Bardowell, who welcomed Sime with a two-out, two-run homer in the first inning, is 23.
"I feel like it can only help me, being able to face guys that are so experienced," said Sime, the fifth-youngest player in the league. "They're not chasing pitches in the dirt as often. I've got to come in attacking the zone and trust myself even more now."
The Louisiana State commit finished the night after allowing four earned runs on four hits and a walk with five strikeouts over 4 2/3 innings. Neverthless, Sime's fastball stole the show -- sitting 97-99 mph and reaching 100.9, the fastest-recorded pitch in the league's history.
Sime's tools are undeniable. The 6-foot-4, 235-pound Gatorade New York Player of the Year lights up radar guns, routinely working in the upper 90s with a fastball that earns a 70-grade tool. His slider sits in the low 80s and has grown sharper over the past year.
Much of his development stems from his work at Elite Performance in New York -- a facility he credits with helping him maintain and build his velocity.
"I work out there pretty much every day in the summer and the offseason," Sime said. "Just sticking through and through with my program … and getting ready for that day [that I'm pitching]. The results always show, so I'm thankful for that."
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Sime has also nurtured his game through MLB Develops, a suite of initiatives designed to grow the sport and provide high-level instruction, mentorship and exposure to amateur players -- particularly those from underserved communities. The right-hander has participated in events such as the Breakthrough Series (2023), Dream Series (2023) and the High School All-American Game (2024).
"A bunch of those coaches that have played in the big leagues and have went through it," Sime said, "they gave us a bunch of advice on how to carry yourself."
That experience has helped prepare Sime for his time in Trenton, and he's not the only Develops alum with the Thunder. The roster includes Carsten Sabathia and Jaden Sheffield, the sons of former frequent All-Stars CC Sabathia and Gary Sheffield, as well as fellow prospect Daniel Corona.
"I've grown really appreciative of that network over the years," Sheffield said. "Being a minority in baseball, you bump into guys across the country you met at the Hank Aaron Invitational. It's a brotherhood -- we always know we've got each other's backs."
Now the group is playing under the guidance of first-year Thunder manager and eight-year Major League veteran pitcher Shawn Chacon -- a 2003 National League All-Star -- who offers the Draft League's next wave of talent a lot of insight.
"From what we've heard, the stuff is electric," Chacon said of Sime. "He's got a lot of hype behind him, and you've got to remember he's still a kid, he's a high schooler. But he's well-mannered, polite, the makeup's there. We're excited to see him grow."
There's no guarantee that Sime will be in the Draft League long. With his raw arm strength and stature hints at the opportunity to become the highest-drafted player in the league's short history. The current mark was set in 2023, when the Braves selected Sabin Ceballos in the third round with the 94th overall pick.
For Sime, that kind of spotlight -- which attracted over 7,000 fans at Trenton Thunder Ballpark for the opener -- is one he won't take for granted. And he's hoping to use the Draft League as a place to grow as much as he's using it to showcase an already impressive skill set.
"Being confident and attacking the zone," Sime expressed as his main goal while with the Thunder. "Now I've got to be more of a pitcher and not as much of a thrower."
The right-hander draws a lot from his father, who models a go-getter attitude in life that his son brings to the mound. On the field, Sime Jr. honors his baseball inspiration by wearing the No. 45 on the back of his jersey.
"Gerrit Cole is my kind of pitching role model," Sime said. "Not only because he's a Yankee, but because of the way he carries himself. … He does a great job of slowing the game down and I want to do exactly what he does when he takes control of the game."