AriBall is the collaborative effort of over half of all MLB teams with Ari Kaplan (Caltech Alumni of the
Decade and MLB consultant for over two decades) and Fred Claire (World Series-winning general
manager of the Los Angeles Dodgers and member of the club’s front office for 30 years.)

Media is welcome to use this information. We would ask for a reference and, if possible, a link to


My first introduction to Hyun-Jin Ryu was an article entitled "Dodger's Foolish Investment in Hyun-Jin Ryu will end badly." When I saw him in 2013 Spring Training, I remained unimpressed with his relatively low velocity and an apparent lack of control (I clearly saw an uncharacteristically shaky start). Many scouts voiced concerns about his ability to be more than a long reliever. The overall conclusion of that first article was that "That is an investment of nearly $62 million for a player who is likely going to be a mid-rotation starter, at best."

Technically, Ryu is a mid-rotation starter. But when your rotation is fronted by Clayton Kershaw and Zack Greinke, being the #3 starter is far from an insult. And in fact, based on statistics, Ryu might be the #2.

Ryu came to MLB in 2013 after dominating his opponents in the KBO. The lefty arrived to camp out of shape (and Ryu's normal shape is round), but he worked hard and his results backed him up. Working with a low-90's fastball, low-80's slider and change, and a low-70's lollipop curve, he carved up the league to the tune of a 3.24 FIP, inducing 50% ground balls and striking out 7.22 per 9 while walking 2.30 per 9. Ryu was worth more than 3 wins that year, but that didn't stop some commentators from suggesting that his sophomore season would be a disappointment. In fact, it was anything but. Ryu posted better numbers across the board (except ERA, which was due to sequencing luck). He struck out 8.23 per 9 and cut his walk rate to 1.72 per 9, resulting in a 2/62 FIP that was 26% better than league average.

This improvement, I believe, can be attributed to increased confidence. And I don't mean that in the typical "invent an explanation" way--the changes Ryu made in his approach can be quantified, and paint the picture of a pitcher who felt more at liberty to go after hitters.

First, let's look at a change in Ryu's pitch selection. The charts below show pitch use in 2013 and 2014.

Ryu hasn't added a new pitch, nor has he dramatically changed his distribution. But he did swap some of his changeups for curveballs. In 2013, he threw about 22% changeups, about 10% curveballs; in 2014 there was a 4% swing to 18% changeups and 14% curveballs (he also threw 2% more sliders and 2% fewer fastballs). The drop in changeup use is particularly interesting, because early scouting reports on him indicated that the change was his best pitch, "a legitimate out pitch at the MLB level." This may have been because the pitch is, and I mean this in a good way, exceedingly average. The velocity, movement, and spin on it is pretty exactly that of the average MLB changeup, making it the easiest to scout because it has so many comps. Clearly Ryu did not want to prioritize it quite as much in his second year as he did in his first. Lessening his use of his best pitch seems like evidence that Ryu was more confident in his abilities, and felt more sure that he could use a variety of pitches to get outs.

Increased curveball use resulted in a very interesting pitch mix. Ryu's fastball, curveball, and slider are all worm killers: look at the concentration of green (ground balls) in his spraycharts below. And of course, changeups are one of the most grounder-inducing pitches in baseball. Put it all together, and it's no surprise that about half of the balls in play against him were ground balls.


Groundballs are great. They're especially great if you need to erase a runner on base. But it's even better if you don't let runners on base in the first place. And those groundballs could still find a hole or result in an error (remember that Hanley Ramirez was the shortstop most of the time Ryu was on the mound). Even better, then, if you don't let the batter put the ball in play. As mentioned, Ryu in 2014 cut his walks and increased his strikeouts. It's easy to see how: take a look at his zone charts. Four different pitches across 2013 and 2014, and every one of them went from just outside the zone in 2013 to outside corner in 2014.

Fastballs 2013 vs 2014:



Curveballs 2013 vs 2014:



Sliders 2013 vs 2014:



Changeups 2013 vs 2014:



Overall locations 2013 vs 2014:


The takeaway is that, in his first year, Ryu nibbled around the edges. He had success, of course, but it meant a higher chance of walking the batter. It also speaks to a pitcher who was not quite sure that he could directly challenge his opponents, who thought that he had to stay away from the zone and limit potential damage.

By 2014, Ryu was more confident, more aware that he could dominate MLB competition without nibbling. He kept the ball in his locations (almost always away), but now threw over the outside corner instead of just beyond it. His first pitch strike % went up almost 3 points from 59.1 to 61.7; his zone % from 43.4 to 44.9, and his zone swing % naturally saw an increase from 62.1 to 64.0, yet his zone contact % stayed exactly the same; the end result, of course, was that his whiff rate increased from 8.1% to 8.8%.

Ryu isn't, and will never be, a strikeout machine with whiff rates above 10--but he doesn't have to be. When you take a guy who gives groundhogs nightmares, and then realize that he strikes out a batter almost every inning, the value is obvious. Over his first two years in MLB, Ryu has been one of the best pitchers in the league. After 2014 proved that even when he locates pitches in the zone, hitters have trouble hitting them, we can expect him to have the confidence to further challenge hitters and to continue being the only ace-level pitcher slotted in as a #3 starter.

NOTE: All statistics accurate as of 02/26/14

By Sam Whitefield