This story was excerpted from Alex Stumpf’s Pirates Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

Paul Skenes stared down Paul Goldschmidt in a scoreless game on Tuesday at Busch Stadium with a runner on first and one out. The Pirates’ rookie phenom had retired the Cardinals’ slugger twice, but this at-bat could make or break the game. Behind in the count 1-0, he knew he had to execute right now.

The pitch he chose? It was his hybrid, the splinker.

“It’s my go-to pitch,” Skenes said. “It’s my confidence pitch.”

It worked to perfection. Goldschmidt swung over top on the diving 96.5 mph offering, bouncing it to Ke’Bryan Hayes to start an inning-ending double play.

Skenes has some of the best stuff of any prospect in recent memory. His fastball can ramp up to 102 mph. His slider gets above average spin and horizontal movement. The Cardinals saw the curveball he has in his back pocket plenty Tuesday, and struggled with the change in velocity and movement it brings. But the fact that Skenes’ newest pitch is his confidence pitch gives a taste of how quickly the pitch has evolved, while teasing its potential.

The “splinker” -- a term Henry Davis coined after catching it -- is one of the most unique pitches in the game. Its origins trace back to when Skenes transferred to Louisiana State and wanted to add a sinker to his repertoire, thinking it would play well to right-handers. He liked the pitch going into the season, but didn’t think it was a good matchup for SEC hitters, so he rarely offered it.

That changed once he got into pro ball, and he found a grip that gave it more dive, like a splitter. Now he had the sinker that he wanted for right-handers that could also be an offspeed offering for lefty batters.

So does that make it more splitter or sinker?

“You can call it a sinker, splinker, split, whatever you want,” pitching coach Oscar Marin said. “I call it super deceptive.”

“I still think of it as a sinker,” Skenes said. “It’s funny to see guys swing at fastballs in the dirt.”

Baseball Savant’s pitch tracking classifies it as a splitter, and it might be the best in baseball. Through Skenes’ first six Major League starts, batters are hitting just .073 (3-for-41) against it with a dozen strikeouts. While all of Skenes’ offerings have a whiff rate of at least 20%, it’s the splinker that gets the most swings and misses, registering at a 33.7% whiff rate and a 30% Putaway rate with two strikes.

Going by Baseball Savant’s run value, it’s been worth nine runs, tied for the second most of all splitters in the game (Cal Quantrill of the Rockies has 14 runs, Fernando Cruz has nine). Those pitchers have been in the Majors all year. Skenes’ career is only a month old. Going on a rate of what its run value is per 100 times it’s thrown, it’s the third-most valuable pitch of the game. Yankees closer Clay Holmes’ slider is worth 5.6 RV/100, Mariners lefty Tayler Saucedo’s sinker is worth 5.1 RV/100, and then Skenes’ splinker is 5 RV/100.

“There’s only two people in the league who throw it,” Marin said. “It’s him and [Twins closer Jhoan] Duran. It looks like a heater, and then it’s not.”

Duran’s splitter is the best comp for Skenes’ splinker, mainly because they are the only split-fingers that can be thrown that hard. Skenes’ offering averages a velocity of 94.4 mph, while Duran’s comes in at 97 mph. Duran has the velocity advantage, but Skenes gets more drop (29.8 inches for Skenes, 26.8 inches for Duran). Pick your poison on if three mph or three inches of vertical movement is more valuable.

Marin also pointed out how the pitch comes out of the hand at the same spot his fastball does, which adds to its deceptiveness. Going by its spin-based movement, it spins very similarly to his four-seamer, so it can have a similar flight path. So even if you can identify something that looks like a fastball out of the hand, it’s tough to recognize if it will be a high-spin four-seamer with the illusion of rise or a pitch that’s going to drop.

“You can sell out to that pitch all you want, but it’s gonna be tough to hit,” Skenes said. “That’s how I look at it.”

The league will have to keep working to find a way to consistently hit the pitch, but even if they do, it’s pretty safe to say Skenes’ confidence in it is not going to waver. The first step would be finding a way to identify it out of the hand. Easier said than done.

“It's a unique pitch,” said manager Derek Shelton, “but he's also a unique guy."