Secondary pitches are called that for a reason. Every pitcher at every level of baseball has worked off of his fastball since the beginning of time. Secondary pitches round out a repertoire even if nearly every pitcher in the majors will throw his fastball more than his other offerings. Even a pitcher who has a lights-out secondary pitch—think Chris Sale’s changeup or Noah Syndergaard’s slider—typically throws that pitch no more than 30% of the time. The fastball is the centerpiece of the arsenal.

That’s what makes Lance McCullers’s knuckle-curve so special.

Consider this column an appreciation of the best secondary pitch in baseball. McCullers’s knuckle-curve is a pitch so filthy that it can be his primary offering. To be clear, secondary, in this context, does not mean lesser. With respect to a pitcher’s repertoire, secondary means every pitch that isn’t a fastball. Part of that owes to the fact that few, if any, pitchers can lean on a secondary pitch as the linchpin of what they do on the mound. McCullers is the exception, with his knuckle-curve standing out as possibly the best single pitch in baseball.

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McCullers is off to a great start this season. He has made two starts thus far, allowing four runs on 11 hits in 13 innings, striking out 17 batters while walking two. It may be a small sample, but it’s safe to say that last year’s injury troubles are in the rear-view mirror and McCullers could realistically compete for a Cy Young Award this season. McCullers owes much of his early success this season, as well as his unbounded potential, to his knuckle-curve.

The Astros’ ace has thrown the big, sweeping pitch for more than half of his pitches this season, challenging hitters to force him in another direction. They have been woefully unsuccessful. Of McCullers’s 17 strikeouts, 11 came with a curveball on strike three. What’s more, all but one of those were of the swinging variety. All told, McCullers’s knuckle-curve has a whiff rate of 23.7% through his first two starts. Given that he enjoyed a 15.8% whiff rate with the pitch in 2015, and a 21.8% whiff rate last year, we can say two things with a good degree of confidence. First, he can maintain this rate all season. Second, and most scary for opposing, hitters, the pitch could be getting better.

In his second start of the season, McCullers fanned 10 Royals while taking a no-decision. You might remember seeing them in rapid succession in this week’s Pitching Report.

via GIPHY

via GIPHY

Watching those two GIFs, you likely notice one pitch turning up again and again. A whopping eight of McCullers’s strikeouts against the Royals featured the knuckle-curve as the strike three pitch. This is where the appreciation of baseball’s best secondary pitch kicks into a new gear. We’re going to do our best to highlight McCullers’s five best knuckle-curves from his outing against Kansas City. It will be more fun for us than it was for the Royals, who actually had to try to hit the curveball.

Our first victim is Alcides Escobar, who thought he was getting a fastball, but turned out to be very wrong.

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Next up is Raul Mondesi Jr. Raul’s dad likely wouldn’t have fared much better against this knuckle-curve, which traveled across the entire width of the plate, and then some, from the time it left McCullers’s right hand until it got to Brian McCann’s glove.

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From there, we move on to Brandon Moss. This is an absolutely filthy offering that looks quite similar to strike three on Mondesi. By comparing these two pitches to the one that got Escobar, you can see how McCullers modifies the knuckle-curve depending on the handedness of the hitter.

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Now it’s Salvador Perez’s turn. Perez took McCullers deep on a fastball earlier in the game, but was one of the few Royals to get to the Astros righty. This is also our first look at McCullers out of the stretch. As you will see shortly, the pitch doesn’t lose any of its bite with McCullers forced to ditch the windup.

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Finally, we get to Paulo Orlando. This is a classic case of the pitcher being in control of the plate appearance, no matter the count. At 2-2, Orlando is still completely defensive, evidenced by an emasculated swing. This knuckle-curve started below the zone and nearly bounced in the dirt before getting to McCann. Still, Orlando couldn’t help himself.

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Lance McCullers’s knuckle-curve, the best secondary pitch in the majors, we salute you.