I attended the Oakland A’s game last night, something I do a few dozen times a year, and Sonny Gray happened to be on the mound plying his trade against a talented Anaheim squad. Though he was shaky in the first inning (his career ERA in the first inning is 4.50, so there could be something to that), he settled down to go eight innings with two earned runs, six hits, one walk, and six strikeouts. He was efficient, looked like an ace, and the A’s won the game.

I moved to the Bay Area just before Sonny Gray was getting his first shot in the majors. In relation to how many games I’ve gone to in Oakland, I’ve witnessed an inordinately high number of his starts in person, so I’ve been able to witness how he’s grown and evolved as a pitcher over the past few years. As April comes to an end, I’m confident enough in those changes to finally write about them. To frame our discussion, let’s begin with a chart of Gray’s fastball usage (separated by type), from the time he was promoted in 2013 until now:

It’s been a gradual transition, but Gray has dropped the four-seam fastball more and more in favor of the two-seam fastball. There are a few reasons pitchers generally do this, but it’s usually to get more ground balls, as well as to work with higher efficiency (pitching to contact). The main drawback is usually fewer strikeouts, along with the possibility that you might get hit hard if your two-seamer isn’t very good.

Has the transition worked for Gray? Is he getting more ground balls and more contact? Here’s a table of some select peripherals:

Season LD% GB% FB% Zone% Z-Swing% Swing% Contact% K% BB% 2013 19.5% 52.9% 27.6% 49.4% 53.0% 39.7% 76.0% 25.7% 7.7% 2014 18.5% 55.9% 25.6% 46.5% 58.6% 43.6% 79.6% 20.4% 8.2% 2015 15.5% 46.6% 37.9% 47.3% 63.7% 46.7% 82.3% 18.4% 4.4%

Ground balls are down from his career high last year, though we are still dealing with small sample sizes, so this could certainly change as the season goes on (a look at game logs this season shows he used his four-seamer more in two starts against Anaheim, yielding more fly balls). He’s also inducing more swings at pitches inside the zone this year as well as overall swings, and his contact rate has risen for three years running. For many pitchers, this wouldn’t necessarily be a good thing, but his line drive rate continuing to fall tells us that a lot of that increased contact is likely on the weak side. Even though his strikeout rate has fallen, his walk rate has also come around, which is usually one of the perks of pitching around the zone and trying to induce contact.

An important point to remember is that even the peripheral numbers that have dropped for Gray are still average or above average compared to the rest of the league: for many pitchers, the switch to an approach centered around a new fastball might have some growing pains, but Gray’s two-seamer is a plus pitch, ranking in the 91st percentile of two-seamers for ground ball rate and 80th percentile for whiffs/swing.

Another change has been Gray’s breaking pitches. Here’s another chart, this time showing the usage of his slider and curveball over his career:

Last year, I wrote in the community pages about the changes in Gray’s curveball, in which he moved from more of a 12 to 6 curve to a harder, slurvier offering. There was a period of time in which he was throwing a breaking ball with a range of different speeds and breaks: Eno even wrote a piece a couple of years ago in which he asked Gray about his breaking ball, and Gray said, “I throw a curveball and sometimes just add and subtract — just one grip”.

That adding and subtracting fooled PITCHf/x for awhile, which had trouble distinguishing between the curveball and the other pitch, which looked more like a slider/slurve. However, it appears as if he’s now throwing that second pitch often enough, and has created enough separation in speed and movement, to have another distinct pitch along with his curve. Here’s a GIF from that FG community article, which I include mostly because I enjoy overlaid GIFs, and because it illustrates the differences between the two breaking balls well:

Not hard to see the difference: one is the big, 12 to 6 curveball Gray has become known for, while the other is much more like a slider — harder, with sharp horizontal break away from right-handed hitters. It’s not a surprise that his usage of the slider occurs mainly against right-handed hitters when he’s ahead in the count/has two strikes. What outcomes does he get from the different pitches? The curve usually causes a lot of swings and misses, while the slider yields a lot of weak contact in the form of ground balls and pop-ups.

I would be remiss if I didn’t mention Gray’s changeup, which is a perennial work in progress. To his credit, he keeps working on it, even through some rough outcomes. His usage of the change is down to around 5% this year, so he might be largely shelving the pitch until a future date; as we know, changeups can take a bit more time than other pitches to learn and get a feel for. Needless to say, Gray has never relied on it as a go-to offering, so it would be more of a nice surprise if and when it does come around.

It’s not unusual for a pitcher to make changes like these. Lots of pitchers go from four-seam fastballs to two-seam fastballs, and vice versa, for myriad reasons. What’s a little different about Sonny Gray is that he’s doing this as a 25-year-old, one who was pretty dominant for the past two years on the back of a big four-seamer and a famous curveball. He’s consciously cut back on the use of both of those pitches, and it’s given him more flexibility in the ways he attacks hitters, as well as ability to go deeper into games. Here’s a final table, showing his average length of start in each year of his career, with the caveat that 2015 is still a small sample size:

Season Average Innings/Start 2013 6.0 2014 6.2 2015 7.1

That’s the endgame for all of this: work deeper into games. He did it last night against a good offensive team, and he’s doing it more often in general by using a more mature, contact-based approach to pitching. For a 25-year-old with an electric arm and a great curveball, that’s a little bit of a surprise; but not many 25-year-olds are the ace of their staff.