David Robertson Is Not Throwing Fastballs

In Saturday’s Game 2, David Robertson relieved Tommy Kahnle, who had relieved Luis Severino. Robertson worked two shutout innings, and the first of them was the bottom of the seventh, during which Robertson threw 13 pitches. Here is a log of what they were.

1. breaking ball
2. breaking ball
3. breaking ball
4. breaking ball
5. breaking ball
6. breaking ball
7. breaking ball
8. breaking ball
9. breaking ball
10. breaking ball
11. breaking ball
12. breaking ball
13. breaking ball

Robertson’s first pitch in the bottom of the eighth was a fastball. It was taken for a strike.

Let’s say, hypothetically, that you are a pitcher, and you have a curveball that looks like this.

Would you not want to throw it almost all of the time? Okay, maybe not all of the time. But that’s a pitch you’d want to throw with great frequency, right? Sure seems like it. Robertson has always had a powerful curveball. He’s always thrown it pretty often. Only this year has he practically let it take over. Especially — especially — in the playoffs. In the playoffs, he’s been a whole new pitcher.

Let’s trace this all the way back. Robertson debuted in the majors in 2008. His fastball is classified as a cutter, because it doesn’t have much in the way of horizontal movement. Here is how Robertson’s cut-fastball usage has moved around over time, over the course of the decade.

The pitch has had its ups and downs. Any pitch would. As you look toward the right, though, you see the blue line dropping. For years, Robertson threw about three-quarters cut fastballs. Then he threw about two-thirds cut fastballs. Through last season, Robertson’s career-low cut-fastball rate was 64%. This year, the rate dropped to 51%. All of a sudden, Robertson threw cut fastballs half the time, and breaking balls the other half of the time. That’s not at all something that happens by accident, and you can see how this looked month over month.

There’s a gradual decline in fastball usage. Almost out of nowhere, there’s the emergence of what looks like a slider. Whatever that pitch is looks like it gained some zip in September or so.

Robertson used to be fastball first, curveball second. Late this past summer, it was like he had co-primary pitches, plus this third alternative. I’m not actually altogether convinced what I’m supposed to make of the slider. I’m not sure if it’s actually a separate pitch from the curveball. It’s roughly two ticks faster, with similar horizontal break, but with almost 10 fewer inches of drop. The slider might be a new and separate pitch, or it might just be a way that Robertson deliberately manipulates his curveball. Look, I don’t know. But, regardless, Robertson’s repertoire consists of a fastball type, and breaking balls. And this is how he’s used his pitches in the playoffs. It’s been an even more exaggerated approach.

Robertson, so far, has made five playoff appearances. His highest single-game cut-fastball rate has been 36%, with his lowest rate being less than half of that. To try to simplify everything, here’s a little table, putting together the entirety of Robertson’s year to date.

Again, I don’t know if the curveball and the slider are truly different. Maybe they’re just supposed to be two different curveballs. No matter what, playoff Robertson has thrown some kind of breaking ball 71% of the time. He spent more than half a decade of his career throwing fastballs around 71% of the time. It’s not like Robertson would be the first relief pitcher in the history of the game to prefer his breaking ball over his heat, but for Robertson, this evolution has been dramatic, and this is all happening in his age-32 year. This regular season, Robertson significantly reduced how often he used his fastball. In the playoffs, he’s reduced his usage only further still. It’s like his breaking ball is his fastball, and his fastball is his offspeed.

Over five playoff appearances, Robertson has thrown 10 innings, with five hits, three walks, and 12 strikeouts. Four times out of five, he’s been asked to throw more than one frame, and Robertson has already entered as early as the top of the third. I certainly don’t want to drill this comparison into the ground, but from the Yankees’ perspective, you get the sense they see Robertson as their potential equivalent of last October’s Andrew Miller. And it should be noted that, in last year’s playoffs, Miller threw fastballs just 38% of the time, with everything else being a slider. Andrew Miller isn’t David Robertson, and David Robertson isn’t Andrew Miller, but the more you think about it, why shouldn’t Robertson use his breaking ball like this? Why shouldn’t he continue to be breaking ball first, given how dominant the pitch has been all year? Robertson already plays for the Yankees, a team that’s made a deliberate shift away from relying on the fastball too much. The supportive environment is there, and based on how Robertson has pitched these last few weeks, I can’t imagine there’s anyone with the Yankees wishing he’d stop what he’s doing.

Robertson, of course, can’t prevent the Yankees from being eliminated by himself. He’s a middle reliever, nothing more, and the Yankees need to start scoring runs, post-haste. But should the Yankees make this series competitive, and even should the Yankees advance another round, Robertson’s going to be a critical part of the league’s deepest bullpen. He’s already gotten several important outs, while turning his arsenal upside-down. If Robertson is to throw fewer breaking balls, it’ll be up to the opposing hitters to make him.