Half Season Heroes: Hyun-Jin Ryu

Tuesday’s decision deadline for players who received qualifying offers came and went, and Hyun-Jin Ryu was the only one of the seven recipients to accept. Ryu will get to follow up on a stellar, albeit injury-shortened, 2018 campaign by remaining with the Dodgers for another year, and he will earn $17.9 million while gearing up for another run at the free agent market.

Despite missing more than half the season with a strained groin, Ryu finished as a top-50 pitcher in Roto value (per ESPN), largely on the strength of a 1.97 ERA and 1.01 WHIP. While FIP, xFIP and SIERA all agree that he should have had an ERA in the 3.00-to-3.20 range, they don’t directly take into account Ryu’s history as an above-average strander. His 85.4 percent LOB% from 2018 is bound to regress, but his career rate of 77.5 percent is more than four percentage points above the typical major league average.

If fewer stranded runners leaves Ryu’s ERA in the upper 2.00s, no fantasy owner can rightfully complain. The much bigger concern is that the lefty — who will turn 32 three days before opening day — could have yet another season interrupted by injury. Ryu made 56 combined starts in his first two seasons but missed 2015 due to shoulder surgery, and he has not thrown as many as 130 innings in any subsequent season. He totaled only 82.1 innings in 2018, which qualifies him for this Half Season Heroes series.

The potential for injury is not the only wild card that will make it difficult to project Ryu for 2019. The degree to which he can fool hitters with his cutter will also be an important factor. This may seem odd, given that, of his four most-used pitches, it was his worst in terms of swinging strike rate and wOBA allowed this season. Yet if we are going to pinpoint what made Ryu so much better in 2018, this is where our focus is going to be.

The most obvious way in which Ryu improved was in recording a 27.5 percent strikeout rate. His previous career high was 22.0 percent in 2014, yet he set the stage for this season’s breakout in 2017, when he struck out batters in only 21.4 percent of plate appearances. Last season was when he introduced his cutter, though it was more of ground ball pitch than a strikeout pitch. It was also the year in which his SwStr% took off, as he got far more whiffs on his four-seam fastball than he had in his first two seasons. After compiling an overall SwStr% of 8.1 percent in 2013 and 8.8 percent in 2014, in 2017 (his next full season), that rate shot up to 10.9 percent. Following a similar path, the SwStr% on Ryu’s four-seam fastball increased from 3.7 percent to 5.1 percent to 7.5 percent.

Despite the increase in whiffs, Ryu’s strikeout rate fell slightly from 2014. The uptick in swings-and-misses was offset by a decrease in called strikes. In 2014, Ryu froze batters at a 19.6 percent rate, and in 2017, that rate fell to 18.1 percent.

So here’s where Ryu’s cutter comes into play. In 2018, his called strike rate rebounded all the way back to 19.6 percent, and his cutter was a key part of the bounceback. It was already a pitch that Ryu threw for strikes, and by increasing his cutter Zone% from 48.7 to 55.1 percent, he made it even better in that regard. By decreasing the Z-Swing% on his cutter from 67.0 to 61.5 percent, Ryu was able to achieve the rebound in his called strike rate.

He also continued to advance his whiff rate, increasing his SwStr% from 10.9 percent to 11.6 percent. Ryu was able to overcome a drop in the usage of his changeup (a pitch that produced a 23.0 percent SwStr% in 2018) and a decline in the SwStr% for his curveball (from 11.7 to 8.3 percent) by jacking up the SwStr% on his four-seam fastball to 12.1 percent.

Though he achieved it in different ways in each season, Ryu has settled in with an overall SwStr% in the last two years that is far higher than those he recorded in his first two seasons. Whether or not he can continue to be one of the majors’ better pitchers at freezing batters could ultimately determine whether he will regress as a strikeout pitcher.

The graph below displays the K% and SwStr% for all pitchers with at least 80 innings from the last three seasons, and it shows that Ryu had a much higher K% than the typical pitcher who had a similar SwStr%. Other pitchers who appeared to overachieve as strikeout pitchers, such as Mike Foltynewicz, Rich Hill and Charlie Morton, also boosted their K-rates by being well above-average at getting called strikes. Ryu has a chance to maintain his gains in strikeout rate in 2019, but he may need to keep freezing batters with his cutter in order to do it.

It is hard to have confidence in any sort of dramatic one-year gain, especially when it involves a pitcher in his early 30s, but it would be easier to take that leap if the improvement had its roots in an enhanced swinging strike rate. Thanks to the work of Jonah Pemstein and Sean Dolinar, we can know the reliability of a pitcher’s SwStr% if we know how many pitches they have thrown. Such data are not readily available to assess the reliability of a pitcher’s called strike rate.

Owners will likely be cautious in pursuing Ryu on draft day, solely on the basis of his injury history. In the 2 Early Mocks, Ryu garnered a 200.7 ADP. Given that he is a regression risk as well as an injury risk, that seems fair. If that bodes for how long owners will wait for him when we start to draft for real, Ryu represents an opportunity for owners to add a pitcher with tremendous across-the-board potential in the later rounds.