It is an incredible speed to believe even after witnessing it. Hanwha Eagles closer Kim Seo-hyun (21) struck a top speed of 159 km/h with his fastball. What is even more astonishing is that his changeup was clocked at 149 km/h. With a changeup faster than the fastballs of most pitchers, he amazed everyone once again.
On the 30th, Kim Seo-hyun came in as a relief in the ninth inning against LG, leading 5-2, and closed the game cleanly with a perfect inning, including two strikeouts, achieving his ninth save of the season. His overwhelming pitching completely crushed LG's desire to rally, securing Hanwha's comeback win and their fourth consecutive victory.
The pitching performance was remarkable. Facing LG's fourth batter Moon Bo-gyeong, Kim Seo-hyun recorded a swinging strikeout with an outside backdoor slider after five pitches. He then retired Kim Hyun-soo with a high fastball clocked at 155 km/h on the fourth pitch, and finished the game by striking out Oh Ji-hwan looking with a slider down the middle on the sixth pitch.
With a total of 15 pitches, he threw 11 strikes, showcasing aggressive pitching. In addition to fastballs at a top speed of 159 km/h and an average of 155 km/h (6 pitches), he evenly utilized four types of pitches including changeups and curves (four each) and one slider. While he had previously relied heavily on fastballs and sliders, he displayed the versatility of a five-pitch pitcher that day.
In particular, his changeup was recorded at a top speed of 149 km/h and an average of 148 km/h. The fourth changeup thrown to Moon Bo-gyeong went low and outside, resulting in a foul. Although Moon Bo-gyeong's bat reacted, the timing was off due to the movement of the ball, resulting in a foul ball towards first base. The third changeup thrown to Kim Hyun-soo slightly missed the outer zone and was ruled a ball.
However, the second changeup thrown to Oh Ji-hwan sank low and in, inducing a swinging strike. The fourth low outside changeup was fouled off but was measured at 149 km/h, comparable to the speed of most pitchers' fastballs.
With such great pitch quality and significant ball movement, Kim Seo-hyun is a pitcher who can effectively compete with just fastballs and sliders. However, he is not satisfied and has dedicated time during the last offseason to mastering the changeup. He had a higher batting average against left-handed batters (.269) than right-handed batters (.159) last year, so a changeup was necessary to counter left-handed hitters.
Kim Seo-hyun, who showed exceptional enthusiasm while learning how to throw a changeup from former pitcher coach Choi Il-eon and Koh Young-gyeong (KT) during last year's Premier 12, has used the changeup occasionally this season. Although the rate has not increased significantly, this year, his batting average against left-handed hitters (.100) has dropped significantly compared to right-handers (.167), showing effectiveness.
A changeup is a pitch that disrupts timing, and just because it is fast doesn't mean it is effective. If it is thrown awkwardly, it can be timed for a fastball, but Kim Seo-hyun's changeup features a slight drop, making it difficult to hit squarely. As the quality of his changeup, which curves in the opposite direction of his primary weapon, the slider, improves, opposing batters now have one more factor to consider when facing Kim Seo-hyun. This means he can gain a more advantageous position in future matchups.
As of that day, Kim Seo-hyun marked a 0.57 earned run average with 1 loss, 9 saves, and 1 hold in 17 games this season. He struck out 14 batters over 15⅔ innings, with a WHIP of 0.83 and a batting average against of .125. In the saves category, he climbed to a tie for first place alongside Park Young-hyun (KT) and Kim Won-jung (Lotte). With Hanwha winning more frequently, save opportunities are also arising more often for Kim Seo-hyun.
Being the only pitcher among the ten with four or more saves and a sub-1.00 ERA highlights his uniqueness. On the 25th of last month against KT, he suffered his first earned run of the season, resulting in a loss and ending his streak of 13 scoreless games to start the season, but he quickly rebounded without any ill effects. The next day, he secured a one-run save, and in three games, he pitched three scoreless innings.
This year, he has five one-run saves, handling pressure in tightly contested situations with ease. He noted, "There have been many one-run situations, so I've become somewhat comfortable with it," and added, "As an athlete, I shouldn't only focus on my personal stats. I'm a player who needs to maintain the game, so I try not to think about records."
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