WEST PALM BEACH, FL—For the first time since the inception of MLB’s Spring Breakout prospect showcase, the Miami Marlins had to leave the friendly confines of Roger Dean Chevrolet Stadium. Their top farmhands traveled 15 minutes south to West Palm Beach on Thursday afternoon to face the Houston Astros prospects.
“This is the future of our organization,” said acting manager Jeff Conine following the game. “They are a bunch of good kids, work hard and I think on the pitching side we just didn’t have it today in the strike zone, but we gave them a good effort.”
Here are the takeaways from the 7-6 loss.
Mr. Marlin the skipper
Jeff Conine, who is a special assistant to Marlins chairman and principal owner Bruce Sherman, was the acting manager for the game after Juan Pierre assumed the role in 2025. Although rumored as a managerial candidate in the past, this opportunity arrived unexpectedly. Conine enjoyed the afternoon, but the Marlins Legends Hall of Famer is content with where he is.
“This is a one-and-done,” Conine said. “Unless they ask me to do this again next year.”
Milbrandt dominant in start
Karson Milbrandt, who is Fish On First’s 13th prospect, went three innings, striking out six (all swinging). His fastball velocity topped out at 97.1 mph and averaged 95.6 mph.
Milbrandt executed his strategy perfectly, elevating heaters and burying his breaking stuff, including his relatively new gyro slider, which he developed quickly last season. It has emerged as his best pitch.
Milbrandt’s slider generated five whiffs and recorded three strikeouts. His first slider strikeout victim was Astros No. 5 prospect Walker Janek.
“It’s quickly become one of my favorite pitches,” Milbrandt said. “I like to throw it a lot. Today the feel was a little bit off, but the movement was good, so looking forward to getting that pat down.”
A slight lapse in control aside, Milbrandt looked fantastic.
Multi-hit day for Alderman
Starting designated hitter Kemp Alderman (FOF #10 prospect) went 2-for-3 on Thursday. His single was clocked at an 87.4 mph exit velocity into center field. In the top of the fourth inning, Alderman singled again to drive in Starlyn Caba and Dillon Lewis, extending the Marlins’ lead to 6-1.
Last season between Double-A and Triple-A, Alderman slashed .285/.338/.482/.819 with 22 home runs, 70 RBI, 22 stolen bases and a 135 wRC+. He was named the 2025 Marlins Minor League Player of the Year. This spring, Alderman was with the big league club, and in 11 Grapefruit League games, he went 4-for-24 with one home run. He was reassigned to minor league camp on March 15.
As Alderman rounds out his development in the minor leagues and matriculates to the big leagues, a major focus will be put on his ability to continue to limit strikeouts and boost his walk rate. If both of those factors work out in the 6’3”, 200-pounder’s favor, he could reach a fairly high ceiling as a four-tool threat. A righty-hitting outfielder, Alderman could fill a need for the Marlins sooner rather than later. He will be a name to follow closely as he starts the season with Triple-A Jacksonville.
Mack continues to impress behind the plate
Second-ranked prospect Joe Mack went 1-for-3 at the plate, but it was what he did defensively that impressed. In the bottom of the first inning, with Milbrandt on the mound, Mack threw out Astros top prospect Kevin Alvarez trying to steal second.
“Joe Mack is polished back there,” Conine said following the game. “You see the way he commands the strike zone with his framing and his release down to second base and his discipline at the plate. He’s close, very close.”
In nine spring training games with the big league team, Mack went 3-for-24 with one home run and four RBI. The Marlins optioned Mack to Jacksonville on March 15. He slashed .257/.338/.475/.813 with 21 home runs, 58 RBI and a 120 wRC+ between AA and AAA.
Walks, then walk-off
Overall, it was a rough afternoon for Marlins’ pitching control-wise. As a unit, Miami’s hurlers issued an astounding 18 walks. For context, Miami affiliates had just one game with 16+ walks in 2025; it was a 22-walk game by the Jupiter Hammerheads on April 8 which broke MiLB records.
Aiden May stranded the bases loaded in both of his innings. The Marlins also stranded the tying run in scoring position in the eighth.
Their early lead held up until the bottom of the ninth. Cannon Pickell walked two and allowed a single to load the bases once again for Caden Powell, who walked it off for the Astros.
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Final pitching lines
Karson Milbrandt: 3.0 IP, 0 H, 1 R, 1 ER, 3 BB, 6 SO
Aiden May: 2.0 IP, 1 H, 0 R, 0 ER, 5 BB, 3 SO
Hayden Cuthbertson: 1.0 IP, 0 H, 0 R, 0 ER, 0 BB, 3 SO
Grant Shepardson: 0.2 IP, 1 H, 2 R, 2 ER, 4 BB, 1 SO
Jake Clemente: 1.0 IP, 2 H, 2 R, 2 ER, 3 BB, 3 SO
Cannon Pickell: 0.2 IP, 1 H, 2 R, 2 ER, 1 BB, 1 SO
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