Before he ever signed with the Marlins, righthander Kevin Defrank learned how to throw his slider by watching Sandy Alcantara on YouTube.

The 17-year-old Defrank, who like Alcantara is a native of the Dominican Republic, was throwing a 94 mph fastball when he signed with the Marlins for $560,000 in January 2025.

That looks like money well spent for Miami after Defrank topped out near 100 mph in the Dominican Summer League. He struck out 34 batters in 31 innings while recording a 3.19 ERA in 10 starts.

“I’m not satisfied,” Defrank said in Spanish when asked about his offseason ranking of No. 5 in the Marlins’ system. “The higher I get ranked, the higher I want to go.”

Defrank won’t turn 18 until August but already is listed at 6-foot-5, 235 pounds. He said that doctors have told him he will likely grow to 6-foot-7.

That evokes comparisons with another extra-tall Marlins righty. Six-foot-8 Eury Perez made his MLB debut at age 20 in 2023.

Defrank will report to Jupiter, Fla., in February. It will be his first season in the U.S., but he won’t be alone.

Defrank, an only child, will be moving stateside with his mother Catalina Encarnacion Vicente. His father Kedwi Antonio Defrank Cruz, will stay in the D.R. where he is a factory supervisor.

While mom cooks his favorite meals, Defrank will continue to work on his high-leg-kick delivery and his arsenal that is centered on a four-seam fastball, sweepy slier and outstanding changeup.

Marlins Latin American complex pitching coordinator Royce Carlton predicts that Defrank will have his “coming out party” in 2026 and that his prospect stock will soar even higher.

“I think we have the best pitching environment of any organization in the Dominican,” Carlton said. “We had a handful of guys throw 100.”

Carlton said Defrank is dedicated to becoming great.

“In season, he’ll text me at night when he should be sleeping,” Carlton said. “He’s constantly asking me pitching questions.

“Kevin is also a young leader. He holds his teammates accountable, and he wants the challenge of facing the best hitters.”