Why is Seung Hwan Oh so difficult to hit?

St. Louis Cardinals manager Mike Matheny wasted no time this spring publicly naming Seung Hwan Oh the closer for the 2017 season. After putting up the league’s fifth highest reliever fWAR (2.6) last season, this should really come as no surprise to Cardinal fans. The manager’s decision was made even easier when the possibility of new roles (i.e. fifth starter, “fireman” reliever) opened up for the previous closer, Trevor Rosenthal (here’s to hoping his lat. soreness doesn’t end up being anything too serious). As a reference, I have provided Oh’s 2016 “rookie” season statistics below:

Of the statistics found in the table, there is legitimately nothing to complain about regarding Oh’s MLB debut season. He was much better than average in each category. Beyond what was included in the table, sure, he experienced some good batted ball fortune (namely BABIP), but it wasn’t necessarily an unsustainable amount at .270. His 6.7% HR/FB rate will almost certainly regress (the 2016 reliever league average was considerably higher at 12.0%), but even with this inevitability, he has created enough wiggle room to still remain a successful reliever.

Moving beyond the outcomes Oh doesn’t have full control over (i.e. balls in play), let’s focus on two outcomes he does control: K% and BB%. His strikeout rate was 13th best among qualified MLB relievers, and his walk rate was 23rd best. And when considering strikeout and walk rates, the first logical step is to look at the pitcher’s repertoire. What does he have that makes him so difficult to hit? For Andrew Miller, it’s the slider. For Aroldis Chapman, it’s the fourseamer (and slider). For Dellin Betances, it’s the curveball. So, what is that makes Oh so difficult to hit, you ask?

Remember, regarding horizontal movement in right-handed pitchers, a negative value means arm-side movement, whereas a positive value means glove-side movement.

As you can see, at 93-94 MPH, Oh will not overpower many MLB hitters with his fourseamer. His dragless horizontal movement, while not minimal (think Jason Motte), certainly isn’t Carlos Martinez-like. Yet, when batters swing, they miss, quite frequently, on each of his pitches. Why is that? Unlike most of my pitch-related posts, in which I draw a rough and not necessarily provable conclusion, this one is actually fairly simple. So easy, that I only need two pitches to help illustrate my point.

One At Bat Case Study (via BrooksBaseball.net)

Jordy Mercer may be a below average hitter (89 career wRC+), but at the same time, he is by no means a “free swinger.” For his career, he has posted a below league-average strikeout rate (16.0%) and a roughly league-average out-of-zone swing rate (30.6%). It certainly didn’t help matters that strike one was four inches off the outside corner, but take a look at the two swings Oh induced on pitches even further outside of the strike zone.

These two very different pitches (blue trail: 85.4 MPH slider, pink trail: 94 MPH fourseamer) follow nearly an identical path out of Oh’s hand and remain on this same path for essentially half (or more, it’s tough to tell from behind the pitcher) of their respective flights to home plate. Yet, despite their very similar flights, the slider lands one and a half feet lower in the zone than the fourseamer. Thus, if a hitter is committed to a fourseamer, sees the path of a fourseamer, and swings like it’s a fourseamer, only to find out it’s actually a slider, he has zero chance at making contact.

If you haven’t yet grasped the importance of pitch tunneling, I hope this prime example provided by the Cardinals closer helps in the process of getting you there. No, this post isn’t meant to be a knock on Oh’s raw stuff because it is actually pretty good, but considering he is entering his age-35 season, we have to be realistic in knowing that his raw stuff will only decline from here. It is reassuring to know that he has mastered a plan — pitch tunneling — to overcome said decline.

As always, credit to @cardinalsgifs for the beautiful GIF used in this post. If you aren’t already following him, you should rectify that immediately.