A few weeks ago, I used some basic PITCHf/x information to note that Rick Porcello‘s curveball started to look a lot like Adam Wainwright’s curveball by the end of last season. That’s the kind of thing that’s interesting to me, even if it isn’t particularly interesting to anyone else, and then later it was revealed that Porcello actually used Wainwright’s curve as an inspiration. I wasn’t expecting that. Even though, I suppose, the data had already made the case. But it was a cool nugget to read in the news.

Now I’m going right back to the well, because once I start thinking about pitch comps again, I have a difficult time focusing on anything else. One thing that’s true is that Rick Porcello now throws a curveball that resembles Wainwright’s. Another thing that’s true is that Porcello isn’t the only one. This is all relatively new to Porcello, but there’s a pitcher in Oakland who’s had this kind of pitch in his back pocket for years.

For the trillionth time, here’s a quick explanation of the method: My pitch comps are based on average speed, horizontal movement, and vertical movement. I find the standard deviation for a pitch type within the league, and then I calculate z-score differences between individual pitches and the target pitch being examined. I end up with three z-scores, which I combine into one comp rating. The closer to zero the rating, the more comparable the pitch. My rule of thumb is that a comp rating under 1.0 is pretty damn strong.

I examined all curveballs thrown at least 50 times by starters in 2015. I compared all the curves to the normal Wainwright curve, and as it happens, the pitcher with the lowest comp score is Oakland free-agent acquisition Rich Hill. So, by this method, Hill throws the Wainwright curve, but a kind of crucial difference is that Hill is left-handed. Maybe that shouldn’t be a crucial difference, I don’t know, but it seems like it should matter. Neatly, there’s another name right behind Hill’s in the spreadsheet. You don’t even have to leave the active roster.

A Comparison of Curveballs Pitcher Velocity Horizontal Vertical Comp Score Adam Wainwright 75.2 9.2 -9.0 — Jesse Hahn 75.9 8.7 -8.3 0.8 SOURCE: Baseball Prospectus PITCHf/x leaderboards Velocity in average miles per hour, horizontal and vertical movements in inches.

The left-handed Hill has a comp score of 0.73. The right-handed Hahn has a comp score of 0.78. The difference is negligible, and Hahn wins out on account of his handedness. Hahn’s curveball and Wainwright’s curveball aren’t identical — they’re separated by a fraction of a mile, and by a fraction of an inch in both primary planes. But this is nothing you’d see with the naked eye. By the naked eye, the best Jesse Hahn curveballs look just like the best Adam Wainwright curveballs.

The obvious issue, as always, is that Wainwright consistently throws curveballs that look like his best, and Hahn’s curve is a bit less reliable. An elite-level curve is about more than its speed and its movement, and this is fundamental stuff. But Hahn’s breaking ball has drawn praise for years, and this is one reason to think it’s been justified. It’s a curveball he learned a long time ago.

Hahn picked up and refined his breaking ball playing catch with his dad, and A’s pitching coach Curt Young used the word “electric” as a descriptor. The curveball is a big reason why the A’s aren’t too worried about Hahn presently ditching his slider — the feeling is that avoiding the slider can help keep Hahn healthy, and he has enough stuff in the rest of his pitches. There’s work to do, with the curve, with the changeup, with everything. There’s always work to be done, but Hahn shouldn’t be forgotten, assuming he’s clear to the other side of last season’s forearm soreness.

For visuals, here are two consecutive pitches. You see Hahn use the curve to get a strike, then you see Hahn use the curve to get a whiff. He didn’t always execute this well, but he has shown the ability to move the curve around both inside and outside of the zone.

As Porcello talked about in the earlier linked article, it’s not an easy thing to learn how to command such a big curveball. The break does afford some margin of error, but it’s a pitch that requires mastery if you want to be able to throw it to spots. Wainwright became a master of his curveball in time, but he didn’t have such polish when he was still new to the majors. He needed time, just as Porcello will, and just as Hahn will. But Wainwright is evidence of the upside. This can be a wonderful pitch, and Porcello and Hahn are decently far along. Wainwright didn’t put it all together until he was 27.

If you want a little Statcast note, I can at least tell you this much — Hahn gets more spin on his curve than almost any other pitcher. We could probably already infer that from the PITCHf/x readings, but Statcast provides further support that the pitch has the potential to be dangerous. One just wants for Hahn to stay healthy, and one just wants for him to develop maybe a bit more confidence in his changeup.

There’s some possible risk here. Hahn is backing off the slider because he thinks it could get him hurt. It’s not impossible that the curveball might be in some way related to Hahn’s 2015 arm problems. In that event, I don’t know how best to proceed. For the time being, you hope Hahn has things right, so he can let the curveball fly. His fastballs do what he wants them to do, and his changeup could be his fourth pitch. He has almost everything you could want.

Jesse Hahn has velocity. He has some experience, he has his health, he has an opportunity, and he has Adam Wainwright’s curveball. Wainwright knows better than anyone else how to use it, but you never know when Hahn might find the instructions.