Early in 2017, Seung Hwan Oh Isn’t the Same Pitcher. Blame It On a Malfunctioning Slider

The usual disclaimer: it’s early, and it would be foolish to get conned by mini-sample size tricks.

That said, Seung Hwan Oh isn’t the same pitcher that we watched last season.

Seung Hwan Oh has an 8.10 ERA in 6.2 innings pitched this season.

And that’s a concern. I didn’t say that Oh’s slippage is permanent, and to an extent his numbers are skewed by an unusually high (read: fluke) .370 batting against him on balls in play.

I wouldn’t be so cavalier about ignoring Oh’s early-season form.

What’s wrong, if anything, with the Cards’ closer?

Last season, in 76 appearances, Oh  had a 1.92 ERA and 2.13 Fielding Independent Era. In his first six appearances of 2017, Oh’s ERA is 8.10., and his Fielding Independent ERA is 7.21. After giving up five homers in 79.2 innings in 2016, Oh has been touched for two home runs in 6.2 innings this year.

Is this just a blip, a glitch, or unfortunate randomness? Is it an early drag caused by Oh’s break in routine to participate in the World Baseball Classic? Have hitters adjusted to his deception? Are they seeing the ball better as pitches leave his hand? Is this linked to the lingering impact of the heavy usage in 2016?

Last season, his first in the U.S., Oh ranked 7th among MLB relievers in innings (79.2), 8th in appearances (76), 9th in pitches thrown (1,303) and 16th in most batters faced.

As I mentioned last week, Oh’s velocity is down.

According to Brooks Baseball, Oh’s four-seam fastball is averaging 91.9 mph this season, down from 93.5 mph in 2016. And his key pitch, the slider, is coming in at 84.9 mph after being clocked at an average of 86.2 mph in ’16.

Oh’s strikeout rate is 8.6 percent; that’s down from last year’s 33%

Oh’s swinging strike rate, 18 percent last year, is currently 11%

The contact rate against Oh:  76 percent in 2016 … and 65.6% now

But more than anything, I’m zeroing in on Oh’s slider.

According to Brooks Baseball, Oh got a whiff-swing rate of 45.1 percent on his money pitch last season, and that’s dropped to 31.8 percent in the first two-plus weeks this season.

Hitters aren’t going after the slider as frequently as they did in 2016, swinging at the pitch 48 percent of the time compared to 58% in 2016. And he isn’t throwing it as often for strikes, with a 13 percent drop in strike percentage this season according to STATS LLC.  Last season hitters chased the out-of-zone sliders just under 50 percent of the time; this year that chase rate has plummeted to 31.3 percent.

There are a lot of smart hitters out there. If they can’t hit a guy, they try to come up with a different approach. In Oh’s case, it looks like they’ve refused to jump on his slider, especially sliders that he throws out of the strike zone. These danged hitters are insisting that Oh challenge them more directly this season … and when he does, it’s bad for him and good for the enemy.

Given the diminished velocity of Oh’s slider, and the hitters’ stubbornness in declining to do Oh a favor by lunging for the slider out of the zone, his killer pitch isn’t as lethal.

Last season, in 110 at-bats that ended with Oh throwing the nasty slider, he struck out 47 batters… or 43.7 percent.

This season, in 12 at-bats that have ended on an Oh slider, he hasn’t struck out a single hitter. But the hitters have whomped the Oh slider for a .500 average, two doubles, two homers and a 1.167 slugging percentage … last season they batted .164 with a .246 slug vs. the slider. In 2016 Oh gave up two homers on 110 at-bats that concluded with the slider; this year they have two homers in 12 at-bats against the pitch.

Oh can fix himself by fixing the slider.

Thanks for reading …


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  • Jim Stallings

    So while Oh is struggling why not insert Rosenthal has the closer?

  • Todd Wilhelm

    Do you think there is any chance he injured himself in the WBC? He threw 3 1/3 scoreless innings there in 2 games. It would be interesting to know the speeds of his pitches in that tournament.

  • geoff

    I hate the WBC tournament where it concerns players from my favorite team. It would not surprise me if Oh ended up being the set-up man he was originally brought in to be. I have often wondered if it would be possible to structure a bullpen so that it would be essentially be split in two pieces. In today’s game, starters have basically been trained to look at seven innings as a complete game, so why not just have two groups of three, with one or the other scheduled to pitch every other day, leaving a few extras for anomalies. I can’t remember the last time I saw a Cardinal’s pitcher, or any pitcher, go nine innings. The game has changed, most of the players are millennials and we all know millennials always need help.

    • Big T

      All good hitters adjust to the strengths of a given pitcher. Oh needs to adjust his approach with attacking the hitters differently.

      Bernie makes a valid point on the velo change which causes Oh’s slider not to have the same “biting” action therefor they recognize it and lay off it.

  • LawrenceKScardsfan

    Very interesting. We’ll see. I was never comfortable with Oh has the closer du jour, but he stepped in admirably after the collapse of Rosenthal. But at 34, Oh’s loss in velocity and other issues could be related to age.

    Chapman was my free agent target for this position. Failing to make an offer for Chapman means its Oh or Rosenthal. Let’s hope things even out a bit.