KBO vs. MLB: A Breakdown

The MLB fan's guide to understanding the KBO.

“MLB is like opera … but KBO is more like rock and roll.”

Lotte Giants superfan Kerry Maher

The South Korean baseball league is known for a flashy, high-paced style of play with players swinging for the fences and, when connecting, flinging their bats away in an expression of passion that would instantly clear the benches in an MLB game. In much of recent history, this assertion can be backed up by hard data (and a lot of YouTube videos). Over the three-year period from 2016-2018, the KBO saw an average OPS around .800 and an ERA around five. For context, during that same period, the MLB had an average OPS below .750 with ERAs hovering in the low fours. So when we look at KBO numbers, how do we put them into a context that makes sense to our MLB-primed brain? If we have a .300 hitter in the KBO, how would that compare to a .300 hitter in the MLB?

Before we answer that question, though, we have to discuss some recent developments in the KBO. In 2019, everything changed. While the MLB has been looking for ways to accelerate offense and pace of play, the KBO has been doing the opposite, aiming to provide at least a modicum of relief for its poor pitchers. Ahead of the 2017 season, the KBO announced a tweak to the way its umpires call the strike zone.  However, the effect was short-lived and minimal. Offensive output was largely unchanged.

So, before the 2019 season, the KBO took a leaf out of MLB’s book and made a change to the baseball itself. The league “de-juiced” the baseball by lowering the coefficient of restitution (COR) so the ball wouldn’t travel as far off the bat because it was effectively less bouncy. The effect was immediate and pronounced, with 2019 offensive numbers decreasing significantly across the board from 2018:

KBO League averages, 2018 vs. 2019

That’s a dramatic change — 2019 saw an 18% decrease in total runs scored over the course of the season, which corresponded to a full point drop in ERA. Even more pronounced was the decline in power: a 14% decrease in slugging percentage (a full 65-point reduction, from .450 to .385), led by a whopping 42% drop in home runs. The de-juicing clearly worked, and the 2019 KBO season resembled an MLB season more than it did the previous KBO season.

2020 figures to look like more of the same, so for this article we’ll be comparing the 2019 seasons of the KBO and MLB to help us understand the differences between the two leagues. With the MLB season in indefinite suspension, the freshly minted KBO season has been and will continue getting quite a few eyeballs, so let’s dive into what those numbers might look like.

Note: This is a broad-strokes article just to give a new viewer of the KBO an idea of what to expect. The premise is pretty straightforward. I took the 2019 KBO numbers and compared them to the 2019 MLB numbers. In the case of any counting stats, I multiplied the KBO numbers by two variables: a game adjustment of 1.125 to extend the KBO’s 144-game regular season to the same length of the 162-game MLB regular season, as well as a team adjustment of three to account for the KBO’s league, which consists of only 10 teams compared to the MLB’s 30. For example, there were 12,778.2 IP in the KBO last year, which adjusts to 43,128 — pretty close to the actual MLB total of 43,423.1 IP. Otherwise, I’ll use the per-nine numbers to compare what an average game looks like between the two leagues.

We can start out by taking a look at the average KBO slash line:

Slash lines, KBO vs. MLB, 2019

With the newly de-juiced ball (and the inversely juiced ball in the MLB), the KBO offense is starting to look a lot more like the MLB. The effects have been similar: A dramatic shift in power numbers. In 2019, KBO slugging plummeted to a level far below the MLB, dragging down the overall OPS to below the MLB average. Nevertheless, KBO players still hit for better average and get on base more frequently than their MLB counterparts. While power numbers were most impacted by the de-juiced ball, both AVG and OBP saw a 20-point drop as well. Yes, that’s right — from 2016 to 2018, the league average in AVG was .287. It’s not hard to see why the KBO has established a reputation for offense, but unfortunately for those who just perked up at the beginning of this sentence, those days have passed.

The obvious conclusion here is that the KBO now has more of a small-ball game than the MLB. It’s an assertion that’s backed up when we take a closer look at all of the hits in 2019:

Hits per nine, KBO vs. MLB, 2019

Here’s the hit distribution broken out:

Hit distribution, KBO vs. MLB, 2019

KBO play features more hits than the major leagues, but sadly for the power-hungry among you, they have a much higher frequency of singles. Indeed, while doubles are hit at a similar rate between the two leagues, home runs happen half as often in the KBO. Extra-base hits come out to only 27% of KBO hits, compared to 38% for the MLB.

If this disappoints you, don’t despair just yet. If you can’t knock it out of the park, you have to bring runs in the old-fashioned way —base running. And don’t worry, KBO has lots of it. There were 993 stolen bases in the KBO last season, which adjusts to 3,351 compared to an MLB season. In the MLB? 2,280.

Base running, KBO vs. MLB, 2019

That’s right: KBO players steal bases 47% more often than MLB base runners. It works out that there’s roughly one attempt to steal per game, and while success rates are pretty similar between the two leagues, KBO players are caught stealing slightly more often than in the MLB. They steal bases at almost the same frequency as they hit bombs, which means while there may not be as many epic bat flips as you were hoping for, there’s plenty of action going on around the diamond.

The small-ball game extends to beyond stealing bases. Without being able to rely on the long ball, KBO players have to scrounge up any method they can to get around the bases and back to home plate. On a per-inning basis, the KBO saw vastly larger frequencies of sacrifice flies and sacrifice hits (i.e. sacrifice bunts). Here’s how a few of these stats shake out on a per-nine rate:

Stats per nine, KBO vs. MLB, 2019

Some of these aren’t much of a difference — a slight uptick in the frequency of batters hit by pitch and wild pitches, but nothing particularly significant. There is, however, a decrease in the rate of intentional walks in the KBO that seems worth mentioning. My educated guess would be that the lack of power hitters allows KBO pitchers to pitch with less fear of extra-base hits knocking in RBI against them.

On the other hand, the sacrifice fly and sacrifice hit rate is pretty significant. A 50% increase in sacrifice flies lends credence to the “small-ball” style, while sacrifice hits occur at nearly twice the rate of the MLB. Keep in mind that pitchers don’t bat in the KBO — in the MLB, the difference in the SH rate between the NL (where pitchers hit) and the AL (where the pitchers are replaced by a DH) was enormous. Of the 776 sacrifice hits in the MLB in 2019, 531 of them were from the NL (410 coming from pitchers). It works out to a SH/9 of around 0.22 in the NL, which is still considerably lower than the KBO. Without being able to rely on the long ball, KBO batters use every method and opportunity they get to scrape together runs.

Overall, a KBO team averages scoring 4.61 runs over the course of a nine-inning game, compared to 4.81 for an MLB team. If you’re coming from the MLB perspective, you can expect pretty similar final scores for a KBO game — a point of much relief to the KBO pitchers, who in 2018 collectively gave up an average of 5.64 runs per standard nine-inning game. Of course, the actual runs per game are a bit higher in the case of extra innings, but keep in mind that the KBO has a 12-inning limit in the regular season, so don’t expect any six-hour slogs.

As you might expect by the league slash line, KBO pitchers have to deal with more base runners due to a higher rate of hits per game, along with a few more walks compared to MLB — it works out to about a 5%  increase in league-average WHIP. Luckily, at half the home run rate, KBO pitchers were able to maintain an ERA 7.5% below the MLB league average:

Pitching basics, KBO vs. MLB, 2019

Furthering the trend of less flashy play in the KBO, strikeouts are considerably less frequent in the KBO:

Strikeouts and Walks, KBO vs. MLB, 2019

With nearly identical walk rates to the MLB, KBO pitchers average a strikeout-to-walk ratio just above 2, a 25% decrease from the 2.69 in the 2019 MLB season. With such a low strikeout rate combined with the nearly halved home run rate, the KBO doesn’t have nearly as many of the “three true outcomes” players that fill out the MLB. Innings pitched are strikingly even — 99 MLB pitchers threw at least 126 innings in 2019, which would predict to correspond to roughly 33 KBO pitchers throwing 112 innings after adjusting for the size of the player pool and length of season. The actual number of KBO pitchers who reached that mark in 2019 was 35.

All of this information should give you some inkling of what to expect when watching a KBO game, but it should also hopefully give you a bit of context when looking at individual KBO players. A .300 hitter is not quite as impressive in the KBO as it is in the MLB. A 30 HR hitter, on the other hand, is a bona fide star — only one player crested the thirty dinger mark last year: Kiwoom Heroes slugger Park Byung-ho, who hit 33. In comparison, the MLB had 58 players hit 30 or more home runs. Even when adjusting for a longer season (tweaking the cutoff to 34 home runs or more in the MLB), the MLB had 35 players get there. Six MLB players finished with an OPS over 1.000 in 2019, while only one KBO player did: catcher Yang Eui-ji of the NC Dinos. On the other hand, 23 players in the KBO hit at least .300 on the season, more than the 19 major leaguers who achieved the mark in a much larger player pool.

While MLB steals leader Mallex Smith had more steals (46) in 2019 than the top base thief in the KBO, Park Chan-ho (39, which even adjusted for season length would only be 44), there are more viable stolen base threats per capita in the KBO. Fifteen MLB players swiped 20 or more bags in 2019 — adjusting the cutoff by the length of the season, this corresponds to 18 bags in the KBO. Sixteen KBO players stole at least that many bases, despite having a third of the player pool of the MLB. 33 KBO players stole at least 10 bases in 2019, compared to 35 MLB players who stole the season-adjusted 11 bags. The KBO essentially has the same number of viable threats along the basepaths, despite having a third of the teams of the MLB — a remarkable comparison.

Pitching has similar stories. Only two KBO pitchers (both middle relievers) had a K/9 over 10; compare that to 19 in MLB. The strikeout leader in the KBO was Josh Lindblom, who dominated in 2019, winning the league MVP. He had 189 strikeouts, which would adjust to nearly 213 strikeouts over a 162-game season — a total exceeded by 20 MLB pitchers. A 10-strikeout pitching performance is impressive in MLB, but it’s downright terrifying in KBO play.

While you may not have as many bat flips in the KBO as you were expecting, there will be plenty of action. Take a look at our introductory article on the KBO and choose a team, and check out our coverage of the KBO, including daily and weekly recaps. Browse past or current leaders on Baseball-Reference or FanGraphs, or follow the 2020 season on MyKBO. Watch videos of the recorded Korean broadcast after the game ends on one of their five Twitch channels. If you’re like us, you’re excited to dig into any fresh baseball content.

Featured image by Justin Paradis (@freshmeatcomm on Twitter)

Dylan Burris

Dylan has been a lifelong Chicago Cubs fan since 2015. A graduate of the University of North Carolina, he devotes most of his non-baseball attention to college basketball.

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