Jays From the Couch looks into the possibility of newly acquired reliever, Seung-hwan Oh, having a bounce back season in 2018
In the upcoming Jays from the Couch Guide to the 2018 Toronto Blue Jays (available in both e-book and paperback formats), I examine each batter and pitcher’s fundamentals. The idea is simple enough: the vast majority of plate appearances turn into either a strikeout, a walk or a batted ball. So, to begin, I take a look at a batter or pitcher’s strikeout rate (K%), walk rate (BB%) and performance on batted balls (measured by their wOBA and BA on batted balls). This helps me better understand which outcomes drove their overall performance, and gives me a sense of how these outcomes compare to other players (in terms of rankings or against the league average).
Then, in order to get a better sense of the sustainability of these outcomes, I examine a batter’s rate of swinging at pitches outside the strike zone (O-Swing%), rate of making contact with pitches inside the strike zone (Z-Contact%) and batted ball contact quality (xwOBA and xBA on batted balls). For pitchers, I examine their rate of getting batters to swing at pitches outside the strike zone (O-Swing%), the rate at which batters make contact with their pitches inside the strike zone (Z-Contact%) and the batted ball contact quality they surrender (xwOBA and xBA on batted balls). I got the idea to focus on O-Swing% and Z-Contact% from this Fangraphs post on plate discipline.
As a late arrival, such an examination of Seung-hwan Oh’s 2016 and 2017 seasons has yet to be included in our 2018 Guide. In lieu of that, here’s a post using the same methodology to show just how much upside Oh has for the Blue Jays in 2018 (while also giving readers a taste of what they can expect in JftC’s upcoming guide). The usual caveats apply here. He seems to be dealing with elbow inflammation and was hampered by a minor hamstring problem at the end of last season. He’s also entering his age-35 season. Any of those issues (and more) may end up hurting his chances to bounce back this year. But, at the very least, the statistical case for a bounce back is very strong.
His ERA- and FIP- tell the general story of his MLB career well. Very, very good in 2016. Below-average in 2017. His poorer luck stranding baserunners contributed, in part, to his poorer ERA- (FIP- is not affected by base runners). Another problem for Oh were his relative struggles striking batters out—he struck out nearly a third of batters in 2016, but only a fifth of batters last season (not terrible, but below average for a reliever). Fewer strikeouts generally correlate with more fewer base runners being stranded. Batters appeared to make a lot more contact on his pitches inside the zone last season, likely a key reason for the diminished strikeout rate. I’d guess that his weaker change-up was a factor in this.
On the other hand, he was able to maintain his elite walk rate (20th best among qualified relievers last year), in large part because he still got batters to swing at balls just as often as he did in 2016. His ability to get batters to chase is elite—even in a down year, Oh produced the 15th best O-Swing% among qualified relievers.
With a slightly below-average K% and a well above-average BB%, Oh was able to maintain an above-average K/BB last season, the 45th best mark in the majors. Therein lies one key reason for optimism: while still good, his strikeout-to-walk ratio may have fallen much more than expected given his O-Swing% and Z-Contact%. The ratio between a pitcher’s O-Swing% and Z-Contact% is moderately correlated to their K/BB (the graph below includes data for all qualified relievers over the last two seasons).
In 2016, Oh’s .50 chase-to-zone contact ratio justified his 5.72 strikeout-to-walk ratio. In 2017, while his chase-to-zone contact ratio fell by about a tenth (his .45 mark still ranked 27th among 280 qualified relievers since 2016), his strikeout-to-walk ratio fell by more than a third. While this is a rudimentary way to estimate a pitcher’s “true K/BB”, the trend line suggests that Oh’s 2017 O-Swing%/Z-Contact% justified a higher K/BB—around 4.60. To put more specific numbers on that, let’s say that a 26.2% strikeout rate and 5.7% walk rate would have been fairer, given Oh’s underlying performance. Those marks would have resulted in a 91 FIP- last season, instead of a 104.
So, Oh produced a strong strikeout-to-walk ratio last season, and probably deserved an even better one (at least using our simple approach). Well, the same goes for his batted ball outcomes. They deteriorated much more than the contact quality he gave up would have justified. He added nearly 100 points to his wOBA on batted balls last season, with his BA on batted balls increasing significantly as well. But his xwOBA and xBA on batted balls? Each experienced a much smaller increase from 2016.
The results are negative batted ball differentials that scream bad baseball luck. His xwOBA-wOBA on batted balls was the 28th most negative in 2017 (among 210 relievers with 100+ batted balls against), while his xBA-BA was 13th most negative. His poor batted ball outcomes were key in driving up his ERA- and FIP- last season. His contact quality against was worse than 2016, but still above-average in terms of both xwOBA and xBA on batted balls. Unfortunately for Oh, those batted balls ended up being more productive (to his opponent) than normal, which led to more runs against.
One area that Oh wasn’t exactly unlucky in was the long ball. He gave up twice as many home runs in 2017, with less innings pitched, which saw his HR/9 swell from 0.56 to 1.52. The league average HR/9 among relievers also increased, but only from 1.04 to 1.16. Problematically, his barrel rate nearly doubled, from 2.6% to 4.9% (the league average for relievers each of the last two seasons was 3.8%), implying that the spike in long balls was (at least mostly) justified.
All in all, Oh seems like a reliever with the upside to be elite and a strong chance of being at least average. His strikeout-to-walk ratio was comfortably above-average last season, and his underlying stats suggest it could have realistically been even higher. The contact quality he gave up last season was similarly better-than-average, with bad luck making things appear to be worse. In Oh, the Jays have added a reliever who has fairly recently displayed better-than-average abilities at generating strikeouts, limiting walks and giving up weak contact on batted balls. And for only $2 million guaranteed, with a vesting option for 2019 (so we get to keep him for another relatively cheap season if he performs in 2018).
There’s always more work to do, but the front office can look back at this off-season as mission accomplished. Now, onto the actual playing part!
*Featured Image Courtesy Of DaveMe Images. Prints Available For Purchase.
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