What has led to Kris Bubic’s recent success?

Kris Bubic entered the season as the #3 starter for the Royals, slotting in behind Zack Greinke and Brad Keller and ahead of Carlos Hernandez and Daniel Lynch. At the time, I felt there were better candidates for the rotation. This belief seemed justified early on as Bubic was shelled in his very first start of the season, giving up five runs and failing to complete the first inning. Through his first six appearances, which comprised five starts and one relief outing, he did not look like a major league pitcher: 13.1 innings, 10 strikeouts, 11 walks, five homers allowed, 12.83 ERA, and 8.98 FIP. He was demoted to AAA the day after that relief appearance.

Bubic made three uninspiring starts in Omaha before being recalled to the major league club on June 4. He started that day against one of the best offenses in baseball: the Houston Astros. He didn’t dominate, but he managed five shutout innings against their potent lineup. Overall, Bubic has been much better since returning from the minors, making ten starts with a 3.76 ERA and 4.15 FIP in 55 innings pitched. In that span, he’s struck out 45 batters, walked 26, and allowed five homers. He hasn’t been dominant, but he’s been downright serviceable. So what has changed?

The first thing that jumps out when looking at his stat page is that the peripherals have not improved much. His strikeout rate since returning from the minors is 18.5%. That is an improvement on his early season rate, but remains well below the league average of 22.3% and his 2020-21 rate of 21.0%. His walk rate of 10.7% is worse than average and a hair higher than his prior career rate. The big difference between his early season and recent outings is the long ball. Five homers in 13.1 innings is a huge problem. Although he was somewhat homer-prone in his first two seasons, he ran a 29.4% HR/FB rate in those first six outings. Given the league average is 11.4%, he was due for some positive regression there, though perhaps his recent 8.9% HR/FB rate will come up a bit.

So the peripherals aren’t outstanding, but a 4.15 FIP since his return is solid. We must go deeper still, and take a look at Bubic’s Statcast page. Let’s start with his pitch usage. Remember when the Royals were talking up Bubic’s new slider? That was fun. According to Statcast, Bubic has yet to throw a slider in a game this year, relying on his four-seamer, changeup, and curveball as he did in his first two seasons. Below is a breakdown of his pitch usage between his six appearances before demotion and ten since:

Not a huge change, but Bubic has dropped his fastball and curveball usage slightly and leaned more into the changeup. Bubic’s changeup has been his most effective pitch this year by run value and has always been his most effective pitch for generating swings and misses, so it makes sense to use it more. That said, it’s hardly an elite pitch. Bubic’s change has below average horizontal and vertical movement and relies on location and changing speeds to be effective. An interesting note: Bubic’s four-seamer was his best pitch last year by run value and by far his worst this year. This is despite him throwing it harder and with more movement than ever. Even with those marginal improvements, it’s still below average by both velo and spin. This presents a conundrum: Bubic’s fastball is simply not a good pitch, but he needs to throw it to set up the change since his curveball and changeup have little velo separation.

So Bubic’s pitch usage has changed slightly, while his stuff remains about the same. How about his command? Command is important for any pitcher, but for a guy like Bubic that lacks premium stuff, it is doubly so.

Here we see some positive changes! Since returning from the minors, Bubic has thrown considerably more first-pitch strikes, gotten more swings outside the zone, and gotten more whiffs on pitches in the zone. That has all contributed to a lower walk rate despite him throwing fewer pitches in the zone overall. The stuff hasn’t changed, so it must be a result of better location. In particular, I’d like to look at his secondary offerings:

The differences are subtle but important. Prior to demotion, Bubic’s command with his secondaries was scattershot, with the most common misses being arm-side with his changeup and leaving his curveball up. Lately he’s been much more consistent at locating his pitches in the correct spots: down in the zone with the changeup showing the ability to both throw it for strikes arm-side and look for chases glove-side, and pounding the curveball glove-side down while also being able to drop it in for strikes. Compare his pitch charts for his 81 pitch start against the Yankees in April and his most recent start, an 82 pitch outing against Tampa:

At first glance, he’s out of the zone more in his most recent start. But looking at each pitch individually, it’s clear he’s executing his pitches much better than he was early this season. In that early start, his curveballs were either meatballs or non-competitive pitches, while his changeups were all over the place. Just look at all those arm-side overthrows. In that more recent start, he was working much more east-west with a clear game plan: changeups arm-side, curveballs glove-side.

So just how sustainable is this? The good news is several key statistical indicators don’t show this as fluky. His .313 BABIP against since demotion is actually a bit higher than both league average and Bubic’s career mark, while his 72.7% LOB is right around both. The bad news is his strikeout and walk numbers still leave a lot to be desired, and he’s still giving up a ton of hard contact. It’s hard to see this continuing, especially with his next start coming in New York against the Yankees, who lead the majors in wRC+ and runs scored. Regardless, this is the best ten-start stretch of his career, and though Bubic will likely never be an ace, stretches like this show that he can be an effective major league starter.