How James Paxton Had His Incredible May

In James Paxton’s final start in the month of May, he didn’t have it. Or at least, he didn’t have it like he’d had it before. Nevertheless, over five innings, he allowed just two runs, while striking out five and throwing two-thirds of his 89 pitches for strikes. Paxton has graduated to the point where even his mediocre outings are kind of all right. The four walks in five frames tell a misleading story; Paxton wasn’t wild. Paxton wasn’t wild because Paxton isn’t wild.

Paxton’s month began with 16 strikeouts against Oakland. That game was followed by a no-hitter in Toronto, and then, the next three times out, Paxton issued only one total walk while whiffing 23. Over six starts in May, Paxton went 43 innings and allowed eight runs, with opponents batting .143 and slugging .240. It’s quite possible this wasn’t even the best month of May for any pitcher — Justin Verlander also started six times, and he allowed five runs, to go with a .195 wOBA. But Paxton shook off a roller-coaster April, and established himself as one of the top starters in either league. If, that is, he wasn’t yet established.

Under the hood, as Paxton wrested greater control of his at-bats, he made some changes to his game plan. The month of May saw Paxton throwing a different fastball. And, as well, the month of May saw Paxton throwing a different curve. He does have a third pitch that’s in between the two, but it was the heater and the curveball that drove the bulk of Paxton’s success.

Some of this, we’ve already talked about. I wrote about the game in which Paxton struck out 16 A’s, and what was most notable about that outing was how Paxton’s fastball mostly sat around the top of the zone. As I write this, in the month of May, Paxton’s fastball shows up second among all fastballs thrown by starters, in run value. It’s been an enormously valuable pitch. The A’s game was interesting because, within, Paxton did something he’d seldom ever done. It was fair to wonder whether he’d keep it up. He kept it up.

After that start, Paxton talked about how he planned to throw more high fastballs. He liked how well it worked, after spending most of his career throwing to the lower half. For most pitchers and for most fastballs that aren’t of the sinker variety, whiffs are easier to find upstairs. To move through this more quickly, I’ve prepared a couple of plots, each covering Paxton from beginning to present. These are rolling-average plots, covering 250 fastballs at a time. Look at how Paxton’s fastball has developed, in terms of average pitch height at home plate:

That rise to the right corresponds to the Oakland game. Paxton had flirted with the high fastball before, but he’s never done it like this, for this long. Paxton went up, and, so far, he’s stayed up. Among starters this April, Paxton’s average fastball height ranked him in the 18th percentile. Among starters this May, his average fastball height ranked him in the 86th percentile. Paxton has changed his intent and he’s changed his execution, and for a very similar-looking plot that only supports the one above, here are his rolling-average high-fastball rates, where “high” is defined as above the approximate middle of the zone:

It’s not that Paxton throws the highest-spin fastball in the world. His fastball doesn’t generate an extraordinary amount of rise. Still, the proof is in the pudding — the fastball works best when it’s close to the belt. Hitters had more success putting Paxton’s fastball in play when he spotted it lower. Fastballs like this one are simply overpowering.

So, based on the above, we have a pitcher who’s made an on-the-fly change to his approach. One would therefore be tempted to believe Paxton is better almost entirely because of his heat. But let me point out something else. I’ll go back again to the May pitch-type run values for starting pitchers. Looking at curveballs, Paxton ranks third. There’s another change that’s happened, that’s effectively broadened Paxton’s repertoire.

I can tell you that Paxton simply threw his curve more often in May. It took a bite out of his slider usage. When something like that happens, you can assume it reflects a certain amount of pitcher confidence. The more a pitcher believes in a pitch, the more he’s going to throw it, it stands to reason. When you look at Paxton’s two-strike curveballs, I don’t think anything jumps out.

That looks like what you’d expect — with two strikes, pitchers are looking for putaways, and Paxton has long tried to keep his putaway curveball down. The change is evident elsewhere. Take a look at Paxton’s zero-strike curveballs:

That’s it. That’s the other part of the picture. Recently, James Paxton has shown an ability and a tendency he hadn’t shown before very often. In the past, when Paxton threw a curveball, he threw it low. Frequently, he threw it out of the zone. In May, the two-strike curves stayed out of the zone, but the zero-strike curves were mostly right there. Paxton showed the ability to throw his curveball for a strike. That ability had long eluded him, and when a pitcher can throw a breaking ball for a strike or for a chase, that’s when it becomes truly dangerous. One curveball becomes multiple curveballs. You can’t just rule the pitch out automatically.

Behold Paxton opening an at-bat with a strike:

And behold him ending an at-bat with a very different kind of strike:

Paxton can’t command his curve the way he can command his fastball. Pretty much no one can command his curve the way he can command his fastball. A curveball comes with a far greater degree of difficulty. Still, there’s better curveball command and there’s worse curveball command, and Paxton’s curveball command has seemingly moved up a couple steps. Or maybe it’s just a different plan, I don’t know, but one way or another, you can see how the curve interacts with the rest of Paxton’s pitches. If a flame-throwing lefty can throw his curve in the zone, that gives a batter more to worry about in any count. And if said lefty can also throw his curve below the zone, that means a batter can’t just spit on a curve out of the hand. To say nothing of how raising the curveball might pair well with raising the fastball. Paxton is now working at every eye level.

A slider is in there too, and it’s effective. Some people call it a cutter. The label doesn’t matter. Paxton likes all three of his pitches. Really, with the new development of the curveball, you could say he likes all four of his pitches. With the fastball, lately, he’s been doing something different. And with the curveball, lately, he’s been doing something different. I don’t know which change could be the more important one. I do know that Paxton doesn’t have to choose. It’s on the hitters now to try to keep up. When Paxton is throwing the strikes that he wants, that’s nearly an impossible task.