Rising Star: Karson Milbrandt’s Ascent to Triple-A
Some baseball prospects burst onto the scene, instantly becoming fan favourites and future stars. Others, however, take a more measured approach, needing time to hone their skills and find their rhythm before truly shining. Miami Marlins prospect Karson Milbrandt firmly belongs in this latter category. After a stellar performance in Double-A this season, where he posted an impressive 1.34 earned run average (ERA) and struck out 70 batters in just 47 innings, the Marlins’ No. 9 prospect according to MLB Pipeline is now set to make the leap to Triple-A.
Milbrandt, a former third-round high school draft pick, initially faced challenges navigating professional lineups. However, with each passing season, the fast-rising right-hander has demonstrated remarkable growth, inching closer to his Major League Baseball dream.
Jacksonville Gears Up for Milbrandt’s Arrival
For any MLB franchise, the ultimate hope is to see their drafted amateur arms develop consistently and improve throughout their careers. Karson Milbrandt has become a prime example of this steady progression since first donning a professional uniform in 2022. During his inaugural full season in professional ball, the 6’2″ hurler logged 95.1 innings across both A-ball and High-A. In that span, Milbrandt issued 50 walks, maintained a .258 batting average against (BAA), and recorded a 4.74 Expected FIP (xFIP).
While his raw talent was evident, the Marlins’ farmhand struggled to generate consistent swings and misses in 2023, with opponents making contact on 83.7% of pitches thrown in the strike zone. Milbrandt saw improvements in his ERA and xFIP in 2024, but it wasn’t until 2025 that his potential truly began to materialise, making it clear Miami had unearthed a gem in their former third-round selection. Following a delayed start to the season due to an elbow injury, Milbrandt showcased his development by striking out 101 batters and pitching to a 3.20 FIP over 77.1 innings in High-A to kick off 2025. This outstanding performance earned him a well-deserved promotion to Double-A late in the season.
Milbrandt concluded the 2025 season with an 8.4 strikeouts per nine innings (K/9) rate and a 2.40 xERA in his initial 10.2 innings at the Double-A level. By this stage, MLB Pipeline had ranked Milbrandt as the Marlins’ 18th-best prospect. However, a successful stint in the Arizona Fall League at the end of 2025 solidified his status as a player on the rise, poised to climb those prospect rankings significantly in 2026.
This projection has indeed come to pass for the Marlins, a team that has already seen multiple prospects make their Major League debut this season. Milbrandt’s arsenal features a fastball that can reach 99 MPH, typically sitting around 95 MPH, complemented by a potent slider, cutter, curveball, and changeup. Crucially, he has refined his command, leading to increased swing-and-miss rates and a higher groundball percentage. Prior to his recent call-up to Triple-A, the right-hander was dominant, boasting a 1.34 ERA, 70 strikeouts, a 3.26 walks per nine innings (BB/9) rate, and an impressive 57.4% groundball rate.
Decoding Milbrandt’s Advanced Metrics
Now that Milbrandt is set to compete at the Triple-A level, Marlins faithful will have the opportunity to scrutinise his pitching data more closely. Even without comprehensive Trackman data for every pitch this season, the available metrics paint a clear picture of why he is considered a top-tier right-handed pitching prospect. According to TJStats, Milbrandt ranks in the elite 99th percentile for whiff rate (42.6%) and swinging strike rate (20.4%) among all Double-A pitchers who have faced at least 150 plate appearances. He also stands out in the 98th percentile for Called Strike Plus Whiff percentage (CSW%) at 36.9% and the 96th percentile for Weighted On-Base Average (wOBA) at .246.
Milbrandt’s Double-A statistics also highlight his effectiveness against both right-handed and left-handed hitters. TJStats places the NL East prospect in the 99th percentile for strikeout percentage (K%) against lefties and the 98th percentile against righties. His repertoire consistently generates swings and misses from hitters on both sides of the plate, with a swinging strike rate exceeding 20% against both groups.
Areas for Refinement at the Next Level
While Milbrandt’s progress has been undeniable, there is one specific area to monitor as he transitions to Triple-A: his ability to induce chases on pitches outside the strike zone from left-handed hitters. Prior to his promotion, Milbrandt ranked in the 99th percentile for Outside Swing Percentage (O-Swing%) against righties (37.3%). However, this metric dropped to the 28th percentile against lefties (26.7%). This disparity contributed to a nearly 10% higher walk rate against lefties (14.1%) compared to righties (4.4%), according to TJStats.
Ultimately, Karson Milbrandt has demonstrably proven his capacity to make the necessary adjustments to elevate his game. He now faces the challenge of implementing these refinements against a more seasoned level of competition at Triple-A, a crucial step in his journey towards the Major Leagues.
