What happened to Jun-Seok Shim?

Following the 2024 MLB trade deadline, it was a consensus among insiders and fans alike that Peter Bendix and the Miami Marlins walked away as one of the biggest winners.

While the first-year president of baseball operations sent away some key contributors and fan favorites at the big league level, those transactions brought back impact talent that was sorely needed in Miami's farm system. Deservingly so, power bats Deyvison De Los Santos and Agustín Ramírez and potential front-of-the-line arms Robby Snelling and Adam Mazur got the most attention from the general media.

Bendix's second-to-last trade of the day, though, was perhaps the most fascinating. During batting practice at the now-disfigured Tropicana Field, the Marlins' home run leader at the time of the deadline, Bryan De La Cruz, got word he was headed to join the playoff push in Pittsburgh. Coming to Miami in return was Pirates #25 prospect Garret Forrester and #19 Jun-Seok Shim (as ranked by Baseball America).

The term "lottery ticket" gets thrown around often in reaction to deadline deals. Generally, it is used to describe a lower-level prospect who could end up being great, but has to overcome many question marks just to reach the majors. Shim fits the bill as well as anyone. Think Powerball ticket.

Coming out of South Korea as the top prospect from his country in the 2023 international signing period due to "his combination of physicality, polish, and present stuff", Shim inked a $750k deal with the Pirates. MLB Pipeline pegged Shim as the #2 pitcher in his class with high praise for his fastball that sat mid-90s and hit triple digits, coupled with two solid offspeed pitches. The only concern at the time of the signing? An elbow injury back in 2021. Unfortunately for both Shim and Pittsburgh, it was a sign of things to come.

Shim's debut season in the Pirates organization was cut short due to a right pectoral strain, another injury to his throwing arm at just 19 years old. In 2024, a few months before he was moved south, a shoulder injury sidelined Shim for the entirety of the season. Still, it was easy to dream on a 20-year-old, 6'4" arm who had flashed such talent coming to a organization with a track record like Miami's, even if he had only thrown eight innings as a professional.

On September 21, the Marlins announced Shim was headed out west to the Arizona Fall League as the youngest of the Marlins prospects. It'd be his first in-game action since he took the mound for the FCL Pirates in August 2023.

Now in mid-November, the dust has settled. In just five innings of work for the Peoria Javelinas, Shim's first impression as a member of the Marlins left plenty to be desired.

What went wrong?

In all six appearances, Shim struggled with command. Whether it was missing down the plate leading to hard contact or an astounding 37.5 BB%, the righty simply couldn't spot his pitches. Even in his final outing on Thursday, when Shim punched out three batters in an inning, he still allowed two baserunners on free passes.

When you couple Shim's lack of command with a significant drop-off in quality of stuff, eleven earned runs across just five innings is the result. Rustiness was expected, but the degradation of his velocity was alarming. There is Statcast data available for three of Shim's appearances. His best fastball registered at 93.5 mph. He averaged 92.0 mph with a spin rate just below 2,000 RPM. Among right-handed MLB pitchers from the 2024 season, those data points are most comparable to journeyman Aaron Brooks.

The silver lining is that while Shim's performance in the desert was extremely underwhelming, it was his first time seeing live batters in games in over 15 months. These type of setbacks happen, especially in small sample sizes. Additionally, Shim's final two outings were easily his best, allowing no earned runs in two innings with five strikeouts.

Shim can use the next couple of months to rest, recover and prepare for what he and Bendix and Co. hope is his first full season of healthy baseball stateside. Shim is expected to start 2025 in Jupiter, either with the FCL Marlins or Low-A Hammerheads.

Interested in learning more about the Miami Marlins' top prospects? Check out our comprehensive top prospects list that includes up-to-date stats, articles and videos about every prospect, scouting reports, and more!