What To Expect From Sung-Bum Na

In recent days, the NC Dinos have asked the KBO to post outfielder Sung-bum Na 나성범. Once MLB and the KBO make the posting official, big-league clubs will have 30 days to sign the 31-year-old outfielder. Na’s posting isn’t official quite yet — neither is Ha-seong Kim 김하성’s — but should be after the Dinos send MLB additional medical information.

Na has had a decorated career in South Korea. He’s a six-time All-Star, two-time Gold Glove winner, and annual MVP candidate. He’s won Gold in the Asian Games and starred on this season’s Korean Series winner. A .317/.384/.542 career hitter, he’s notched a 150 wRC+ in two of his last three full seasons, and probably would have made it three out of four had he not blown out his knee in May of 2019.

That injury is the main reason you’re reading this article now instead of a year ago: Na has long dreamed of playing in the majors, and he’d originally planned to test MLB waters following the 2019 season. At the time of the injury, he was loosely considered a five-tool player. He’d already shifted from center to right field at that point, but he was good there on the strength of above average speed and a strong arm. He wasn’t quite the same guy in the field last season, as he played more DH than right, and only attempted four steals.

Fortunately, the bat is the real calling card here, and his numbers at the plate looked no worse for wear. If anything, he found his power stroke while sidelined:

Na has a strength-based power profile. Mechanically, his front foot drifts noticeably toward first base when he swings, and he generates his power from keeping his front side closed as long as possible, before snapping open as his barrel enters the zone. At six-feet, 220 pounds, he’s one of the bigger guys in the KBO, and he uses the leverage in his frame to create torque. He’s swing-happy, takes a big cut, and goes for broke just about every time the bat leaves his shoulder. If you’ve paid any attention to baseball these last few years, this should be a familiar offensive profile.

As you might have inferred, there’s a drawback to this kind of swing and approach: Na strikes out a lot and despite running a bunch of deep counts, he doesn’t work many walks. That’s a problem, because he’s having those issues in the KBO, and the pitching in Korea is quite a bit worse than what he’ll find in the States. There are a handful of MLB-caliber arms in the KBO at any given time, but also a bunch of soft-tossing righties armed with nothing better than a mid-80s fastball and a lollipop curve. Striking out a quarter of the time — the fourth highest figure in the circuit last year — against that kind of pitching is a big red flag.

Na is often late on low-to-mid 90s fastballs, particularly if they aren’t at the very bottom part of the strike zone. Worse, he’s easily lured down and out of the zone, where even mediocre KBO breaking balls can entice him to chase pitches in the dirt. He generally sits fastball, and to be sure, he can turn on and drive good heat if it’s down and in. Ultimately though, Na does most of his damage on mistakes.

How does all of that translate? For one scout who has watched him in recent years, not particularly well.

“I don’t have real high hopes for him in MLB,” the scout said. “He doesn’t have any specific separating tool outside of maybe his arm. His power is not outstanding for MLB, he’s not the type of defender you could see filling in at center. There’s a real question of how he’d do against velocity and quality breaking balls.”

Statistically, there aren’t a whole lot of direct comparisons to make, as the list of position players who have moved directly from the KBO to the major leagues in recent years is very short. There are only five Korean players who have done so in the last decade, and Dae-Ho Lee 이대호 is an imperfect comparison because he spent two years in Japan’s NPB before signing with the Mariners.

Jung Ho Kang 강정호 hit well for two years, but he was also more athletic and just 27 when he debuted. None of the bat-only players who arrived in their 30s fared nearly as well in MLB as they did in the KBO. And of the three who garnered significant playing time (Lee, Hyun Soo Kim 김현수, and ByungHo Park 박병호) all struggled mightily once the league figured them out.

It wouldn’t surprise me if Na’s big league career follows a similar pattern to Lee and Kim: A short-term deal, a roster spot out of spring training, perhaps a hot start to his career as pitchers learn where they should and shouldn’t challenge him.

Ultimately though, while I think he’s rosterable, Na will likely not be an impact player. In an optimistic scenario, he could manage a wRC+ on the right side of average as a bat off the bench, perhaps even in a platoon if he handles velocity better than I anticipate. But against premium gas and better spin than he’s ever seen, I think it’s more likely that he’s an up-and-down player. There are just too many ways to get him out.

With that in mind, I expect the bidding to be pretty low: A one-year, six-figure deal seems about right. A source I spoke with suggested that those terms will likely fall below Na’s expectations (he’s represented by the Boras Corporation, for what it’s worth) and that he may stay put if the money isn’t right. Time will tell.