This Marlins Prospect Continues to Boost Stock With AFL Gem Performances

This prospect showed his high caliber swing-and-miss stuff in the desert.

Mar 17, 2025; Jupiter, Florida, USA; A general view of the cap worn by the Miami Marlins for St. Patrick's Day against the New York Mets before the game at Roger Dean Chevrolet Stadium. | Rhona Wise-Imagn Images

The Arizona Fall League offers a great opportunity for both hitters and pitchers to gain more in-game experience before the offseason. Miami Marlins prospect Karson Milbrandt has used that opportunity to show some of the best swing-and-miss stuff in all of minor league baseball.

In Milbrandt’s most recent start Thursday for the Mesa Solar Sox, the right hander struck out seven batters in his three innings pitched. He would allow just one hit and one earned run over the course of his outing.

He struck out some of the game's most notable prospects in his most recent performance. In the top of the first, he struck out Orioles prospect Enrique Bradfield Jr. on three pitches. Two four-seam fastballs at 95.5 and 96.2 mph into an 85.2 mph slider.

He’d cap off a strong first inning by striking out MLB Pipeline’s No. 48 overall prospect Alfredo Duno. He showcased his strong cutter in this at-bat, as well as his curveball before going back to the four-seamer for strike three.

Karson Millbrandt sets down Alfredo Duno.

Cutter at 88
Curveball at 84
Fastball at 96
Fastball at 96

Pushing close to 2900 RPM on the breaking balls. pic.twitter.com/djv89aSlJZ

— Aram Leighton (@AramLeighton8) October 16, 2025

Milbrandt would go on to strike out the side in the second before going out for his third inning of work. In that third frame, he’d add another two strikeouts to bring his total to seven on the start. He’d strike out Orioles prospect Ethan Anderson before striking out Alfredo Duno again.

He sat Duno down for the second time on four pitches, this time working three cutters straight after a 94 mph fastball for the strikeout. Milbrandt would walk three batters, but the stuff shows that when it’s on, it’s very hard to barrel up.

Milbrandt’s strikeout total now sits at 11 this fall, good for third across all AFL pitchers. The 21-year-old is no stranger to high strikeout numbers. Out of all pitchers in the Marlins organization, Milbrandt finished fifth with 113 total punch-outs.

Karson Milbrandt brings the heat in the desert.

The @Marlins' No. 18 prospect strikes out seven over three innings in the Fall League: pic.twitter.com/DtHBTQ8yhM

— MLB Pipeline (@MLBPipeline) October 16, 2025

It’s encouraging to see Milbrandt maintaining the high strikeout numbers this fall. The only thing more encouraging would be to see the overall control improve. While it has only been two outings, Milbrant’s walked five over his near seven innings pitched.

Over the course of the 2025 season, Milbrandt posted a walk rate of 12.3%. If the control can improve the rest of this fall and throughout the offseason, 2026 can be an incredibly productive season. 

There’s still plenty of room for growth for Miami’s No. 18 overall prospect by MLB Pipeline. For a pitcher who struck out hitters at a 29% clip in 2025, the ceiling is high.

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