Early KBO home run derby has fans, players talking about reasons why

Home runs are flying out of KBO League ballparks early and often this season, raising a familiar question among players and fans — is the baseball juiced?

KT Wiz’s Heo Kyoung-min hits a game-tying two-run home run with two outs and a runner on first in the top of the sixth inning against the LG Twins during a KBO League game at Jamsil Baseball Stadium in Songpa District, southern Seoul, on March 29. [NEWS1]

Home runs are flying out of KBO League ballparks early and often this season, raising a familiar question among players and fans — is the baseball juiced?

The numbers explain why the conversation has started. During the preseason, there were 119 home runs in 60 total games, an average of 1.98 per game. That marks a clear jump from the rates of 1.72 in 2024 and 1.26 in 2025.

The long ball trend carried into the regular season that opened Saturday. Across the opening two-game series, hitters combined for 24 home runs in just 10 games. Sixteen came in smaller, hitter-friendly parks in Daegu, Incheon and South Gyeongsang's Changwon. Even with that context, however, the high total stands out given that teams typically open with their top starting pitchers.

Fans noticed first. Some pointed to balls clearing the fence off swings that didn’t look like home runs. Others questioned whether the ball itself had changed.

On the field, the reaction sounded more observational than accusatory.

KT Wiz manager Lee Kang-chul said outfielders have also picked up on the difference.

“Outfielders notice it the most,” he said. “There’s talk that balls are traveling two or three steps farther. Even LG [Twins’] Park Hae-min, who is a strong defender, couldn’t track some balls properly.”

“It feels like the ball is carrying farther,” SSG Landers manager Lee Soong-yong added.

Hanwha Eagles’ Chae Eun-seong gives a thumbs-up after hitting a solo home run with one out in the bottom of the fourth inning against the Kiwoom Heroes in a KBO League regular-season opener at Hanwha Life Ballpark in Daejeon on March 28. [NEWS1]

Yet the KBO released its first test results Monday and did not find evidence of a change.

The league examined 60 balls collected at random from five batches. The average coefficient of restitution measured 0.4093, within the approved range of 0.4034 to 0.4234. That figure is lower than the 0.4123 recorded in the first such test in March of last year.

The physical specifications also do not support the idea of a livelier ball. The balls tested were slightly heavier than before, by 1.18 grams (0.04 ounces), and slightly larger, by 0.1 millimeters (0.004 inches) in circumference. An increase in both areas typically reduces distance due to increased air resistance.

If the ball itself is not the reason for the sudden rise in dingers, several other factors could explain the increase.

The official ball for 2020 KBO League games is seen in this image from the Korea Baseball Organization's website. [SCREEN CAPTURE]

Hitters have adjusted to the automated ball-strike system (ABS), which was introduced last season. Pitchers attacked the upper part of the zone more frequently under ABS, and early on, hitters struggled with high breaking balls.

That has shifted. Hitters are now more aggressive against high pitches, which are more likely to produce home runs when lifted.

Kiwoom Heroes infielder Choi Joo-hwan said the trend reflects broader improvements.

“I don’t think the increase in home runs comes only from the ball,” he said. “Hitters have built more strength through weight training, and their technique has improved.”

Heroes manager Seol Jong-jin said early-season conditioning also plays a role. “This is a time of year when hitters’ conditioning and strength are at a high level.”

Lotte Giants’ No Jin-hyuk rounds the bases after hitting a solo home run in the top of the fifth inning against the Samsung Lions during a KBO League game at Samsung Lions Park in Daegu on March 29. [YONHAP]

Additionally, weather conditions have favored hitters.

A 10-degree Celsius increase in temperature can add about 2.16 meters (7.1 feet) to a ball’s flight, according to Robert Adair’s “The Physics of Baseball” (1990). Lower humidity can further increase carry.

This March has been unusually warm. Cherry blossoms bloomed about 10 days earlier than usual, and no preseason games were rained out. Daytime highs reached 21 degrees Celsius during the opening series over the weekend.

There is also recent precedent for an early spike.

Last season’s opening two-game series produced 25 home runs. The rate dropped from 1.77 per game in March to 1.48 in April, and the full-season average settled at 1.65, which is in line with recent years.

For now, the early increase remains inconclusive.

The data does not point to a change in the baseball, and similar spikes have leveled off over time. Whether this trend continues will become clearer as the sample grows.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom. BY KIM HYO-KYOUNG [kim.juyeon2@joongang.co.kr]