Kris Bubic Sweepers All Before Him

The Kansas City Royals have an excellent starting rotation. Starting pitching (along with Bobby Witt Jr. turning into Honus Wagner with a mullet, I guess) carried the Royals to the ALDS last year. It’s also why the Royals will be well-positioned in the AL Central race if the Tigers ever realize that they’re not actually the 1975 Reds.

But even in such a deep, well-rounded unit, one man must lead the charge. Is it ace Cole Ragans? No. Is it one of Seth Lugo, Michael Lorenzen, or Michael Wacha, Kansas City’s army of rejuvenated Millennials? Again, no.

It’s Kris Bubic!

After nine starts, Bubic is fifth among qualified starters in ERA, ninth in FIP, and seventh in WAR. That’s first among Royals pitchers (Wacha is down at 12th, a third of a win back, as of this writing), and between Garrett Crochet and Zack Wheeler on the overall leaderboard. I don’t know if this is a kind of figurative language or not, but “between Crochet and Wheeler on the leaderboard” seems like one of the best places a starting pitcher can be.

Bubic is hardly new on the scene. In 2018, the Royals had five picks in the top 58 and tried to kickstart a lagging farm system by using all of them on polished college pitchers. I don’t want to say it didn’t work, but Brady Singer was the best product of that group by some margin.

Bubic already had a shot in the rotation, from 2020 to 2022, and he pitched like he was intentionally trying to piss FIP off: far less than a strikeout an inning, walk rates and HR/FB ratios in the double digits. When I showed up in Baltimore for the Wild Card series last year, I had mentally consigned Bubic to depth arm status, and was intrigued to see him throw scoreless high-leverage outings in both games.

This time last season, Bubic was on the road to recovery from Tommy John surgery. His re-emergence as a one-inning reliever late in the year can probably be attributed to Kansas City’s need for someone, anyone, to get lefties out during the pennant race.

But the Royals do have a growing track record of making bona fide starters out of pitchers a lot of people thought were relievers. Lugo’s initial return to the rotation with San Diego in 2023 was successful, but not Cy Young runner-up successful, for instance. Lorenzen also had varied results in the rotation across brief stints with the Angels, Tigers, Phillies, and Rangers. But the Royals have started him consistently, and been rewarded with a 2.99 ERA in 15 starts and only one relief appearance.

Why not Bubic, then?

Bubic came back from Tommy John surgery as a much better pitcher than before. You hear about guys who throw harder after rehab, and I suppose that’s true of Bubic too, but only by decimals. Not that velocity matters that much; he’s been a finesse lefty dating back to his days at Stanford.

No, Bubic’s advancement was in the softer parts of his repertoire. In the first three years and change of his major league career, he threw a four-seamer, a curveball, and a changeup. That worked for a while, but in 2022, opponents started absolutely crushing his heater. Like, to the tune of a .441 wOBA.

In 2022, Baseball Savant rated Bubic’s fastball 31 runs below average. That made it the worst pitch in baseball, by a combination of ickiness and volume. Not just in 2022, but in any of the past five seasons. Only three other pitches got 30 or more runs from average in either direction, so if you want to conceptualize how big a deal 31 runs is, imagine Logan Webb’s changeup or Dylan Cease’s slider, but the opposite.

If you want to know why Bubic’s fastball turned opposing hitters into Superman, consider the other two pitches he threw at the time. Both his changeup and his curveball averaged around 80 mph, and the curveball’s sharp up-and-down movement made it pretty easy to identify out of the hand. Especially for lefties, who could be pretty sure that anything that wasn’t coming in hard was the deuce, and could be disregarded.

After that debacle, Bubic started tweaking his breaking ball usage. Wouldn’t you?

Bubic was already working in a slider, to some effect, in his brief pre-injury stint in 2023. Then he came out of his rehab in 2024 throwing a sweeper instead of a curveball. Developing a sweeper on a fresh, out-of-the-box UCL is kind of like buying a Porsche on a cold day and redlining it seconds after you turn the key. But what the hell, if they replaced the ligament once they can do it again.

As a one-inning reliever, Bubic went back to three pitches — fastball, changeup, sweeper — in 2024. In 2025, he’s reintroduced the slider in addition to the sweeper, and is also sprinkling in the occasional sinker to lefties. (If he starts throwing a splitter, he can complete the punch card for pitches that start with “s” and end in “r,” which would entitle him to a free milkshake at participating Chick-fil-a locations.)

But consider what he can do now. Here’s the old curveball; it’s pretty, but to my eternal frustration, big and loopy doesn’t always mean hard to hit:

Just adding the slider, with its more subtle movement, gives hitters something more to think about. It’s not as hard as a cutter, but it fills a similar place in Bubic’s repertoire, giving him something to bridge the gap in velocity and movement between his four-seamer and his sweeper:

And in case you missed the curveball, there’s still plenty of Bugs Bunny action in this sweeper, which has genuinely wild side-to-side movement, with a little more velo and a lot less of a pop out of the hand:

This would be slightly easier to illustrate if the center field camera at Kauffman Field weren’t somewhere near the left field foul pole, but I hope the point comes across nonetheless.

But wait, there’s more. Bubic has also overhauled his changeup from his pre-surgery days. Back then, it was slower, closer in velocity to his curveball. See how this one floats?

In the past year, Bubic has started throwing the changeup harder, but with about 300 rpm less spin. That means that even though it’s about 5 mph faster on average, it’s dropping and tumbling more in the distance between pitching hand and plate:

I don’t think Cole Hamels is quaking in his boots, worrying about his place in the Hall of Great Lefty Changeups or anything. But Bubic’s new change has more bite, and crucially is closer in velocity to the breaking pitches he’s throwing now. Then again, I say all that, and opponents are hitting .156 against Bubic’s change this year, and have yet to hit it for extra bases.

I think there’s a little bit of the Lugo approach, where you just keep adding pitches until your Baseball Savant page looks like the selection screen on a Coke Freestyle machine. But even with four and a half pitches (he still doesn’t throw the sinker that much), Bubic is keeping hitters off his fastball. That .441 opponent wOBA off the four-seamer is down to .300 this year, which is more than acceptable for a 92 mph heater without especially remarkable movement.

Once one of the more predictable starters out there, Bubic is keeping hitters guessing. He has the sixth-highest chase rate among pitchers with 30 or more innings this year, and the 19th-smallest gap between O-Swing% and Z-Swing%. (Generally, you want hitters to swing at balls and take strikes.)

Does that mean Bubic’s wizardry will last? Well, the league leader in both of those categories is Aaron Nola. I’m a huge Nola guy in general, but even I’ll admit he’s been absolutely horrendous this year, with an ERA of 6.16 and seven losses in nine starts. Which is to say that there’s confusing the hitter, and then there’s nibbling, and the line between the two can be blurry.

Whether it continues to work or not, Bubic is not in a situation where we’re wondering if his early-season success is a small-sample mirage. It’s pretty clear based on pitch-level data that the guy who got rocked in 2022 is gone, and what we’re looking at now is a completely different pitcher.