Seong-Jun Kim 7/7/26

Monday night Seong-Jun Kim made his second appearance on the mound for the ACL Rangers. Kim signed for $1.2 million out of Korea as a two-way player, and the Rangers are developing him on both sides. Monday night was a throw away outing results wise, but it was interesting to compare the look to extended spring training and try to glean some insight into the Rangers’ developmental plan.

Most notably, Kim’s arm slot appeared lower than my look in extended. I suspect the impetus for the change was improving fastball shape – maybe a lower slot could result in more run to pair with Kim’s SL. The fastball played true in extended and was hit hard in my look. There are tradeoffs to any mechanics change you make, and I think Kim is adjusting to mechanics tweaks. The curveball shape was better in extended, and he had trouble staying on top of it Monday. Kim also had trouble maintaining posture with lateral trunk tilt through release that lead to east/west misses. He also worked slower to home and had trouble repeating in general.

It is hard to be overly critical of a young player splitting time between position player and pitcher reps – especially without knowing how his time is being divided and the team's overall developmental plan. You could still see the athleticism, body control and Kim’s potential as a pitcher. He worked 91-94 and could be feasibly sit mid 90s at maturity as he fills out and refines his game. The slider (79-83) flashed tight 2p break, and the mid 80s splitter had nasty late dive, looking like a good swing and miss offering.