Stephen Kolek Has Provided a Much-Needed Spark to the Royals' Rotation

After losing four in a row and 10 out of their last 11 games, the Kansas City Royals were looking for a spark on Saturday afternoon at Kauffman Stadium.

Nearly 26,000 fans were in attendance, primarily to celebrate "Star Wars Day at the K". That massive attendance helped create an environment far from the sparse, lifeless crowds of the Red Sox series earlier in the week. Furthermore, the Kansas City branch of the "Tarps Off" crew was in full force in the 427-429 sections of the K, which helped bring energy to the stadium in the later innings. Below is a progression of how it grew over the course of the game (from my vantage point in section 418).

However, the main spark on Saturday in the Royals' 5-0 victory over the Seattle Mariners? It was starting pitcher Stephen Kolek, who not only pitched a four-hit shutout but also accomplished the first Royals shutout since Brad Keller did it back in 2020. (That's right, it's been six years since a Kansas City pitcher produced a complete game shutout.)

The Royals now sit at 21-31 and will look to take the series from the Mariners in the Sunday finale. A victory over the Mariners tomorrow would not only improve their record to 5-1 against them, but it would also build some much-needed momentum for the three-game series against the New York Yankees, which begins on Memorial Day.

Let's take a look at not only Kolek's masterful performance on Saturday at the K, but what he's done since joining the Royals last year. Furthermore, I will also dive into his outlook with this club for the remainder of the 2026 season, as they look to get back into playoff contention. 

Kolek Works Efficiently in Shutout Win

What's most remarkable about Kolek's performance against Seattle on Saturday was that it wasn't an outing with a ton of strikeouts. He only struck out two batters, both coming in the 8th and 9th innings, respectively. That said, Kolek's ability to work efficiently and quickly through at-bats, especially in the early innings, helped keep his pitch count reasonable for a shot at the shutout.

In his stellar outing, Kolek threw 108 pitches and didn't throw more than 18 pitches in an inning. Furthermore, he maintained a consistent velocity throughout each inning, which helped him remain effective against a dangerous Mariners lineup. Below is his pitch count and velocity by inning, via Baseball Savant.

After an eight-pitch first inning, Kolek threw more than 14 pitches in an inning only once, which was 18 in the fifth inning. Even though he gave up four hits and a walk, the 29-year-old was able to navigate through innings with runners on base thanks to stellar defense by the Royals. They turned two double plays in the game, including a key 3-2-5 in the 2nd that prevented Luke Raley from scoring at third with less than two outs.

When looking at Kolek's TJ Stuff+ summary from this outing, it didn't have the "look" of a traditional shutout. 

The former Texas A&M product didn't generate a ton of chase or whiff in this outing, as illustrated by his overall 24% CSW. Additionally, he had only a 46.3% zone rate, which is slightly below the league average. And yet, despite these issues and a mediocre TJ Stuff+ profile, he limited hard contact (via xwOBACON), which proved to be the most important trait today. 

Kolek generated a .227 overall xwOBACON with his four-seamer (.143) and sinker (.165), his two most-thrown pitches on Saturday, both sporting xwOBACON marks under .200. He had an overall TJ Stuff+ of 96 on Saturday, with only his slider sporting a TJ Stuff+ over 100. That seemed to affect his ability to generate chase (25.9%) and whiff (14%), but did not prevent him from achieving efficient results.

The former Dodgers 11th-round pick was fearless in the zone, as illustrated in his pitch type chart below.

However, as seen in his corresponding pitch description chart, Seattle hitters were unable to consistently square up on Kolek's pitches, even if they primarily sat in hittable areas of the strike zone. 

A big key for Kolek was that he was able to generate contact that just wasn't barreled by Mariners hitters on Saturday. Even though his velocity wasn't elite, Seattle seemed to struggle with timing. As a result, a lot of balls were hit in the air and to right-center, especially. That helped Kolek produce many flyball outs, as seen in the spray chart below from today's game via Savant.

Only one ball was hit with authority, which was a double by Raley (who had three hits of the Mariners' four hits against Kolek). Everything else? Well, the Mariners ended up hitting a lot of groundballs and flyballs to the right side of the field. Furthermore, not many of those balls were hit all that hard. That is illustrated in his radial chart below via Savant. 

Much has been made of Seth Lugo and his pitch efficiency in his 2+ seasons in Kansas City. However, on Saturday, Kolek showed that he may be the Royals' most efficient pitcher in the rotation, and his shutout, the first for Kansas City in six seasons, illustrated that.

Kolek Has Thrived In Kansas City (And His Fastball Improvement Has Been Key)

When the Royals acquired Kolek and fellow Padres pitcher Ryan Bergert from San Diego in exchange for catcher Freddy Fermin at last year's trade deadline, the Royals knew they were getting a pitcher with some big-league success.

Kolek pitched 79.2 innings with the Padres in 2025 before getting traded over to Kansas City. In 14 starts, he posted a 4.21 ERA, 1.31 WHIP, and 4.28 FIP. He also generated a 16.7% K%, 7.7% BB%, and 8.9% K-BB% with San Diego. 

Even though he started in Triple-A Omaha, when Kolek made his Royals debut, he proved to be even more effective down the stretch in 2025. 

In five starts and 33 IP, he posted a 1.91 ERA, 0.76 WHIP, and 2.71 FIP. His K% remained stable at 16.8%, but his BB% dropped to 4%, thus increasing his K-BB% to 12.8%. 

As a result, in 112.2 IP, he posted a 3.51 ERA, 1.14 WHIP, 3.83 FIP, and 10% K-BB%. He did this with slightly subpar TJ Stuff+ (96), as well as mediocre chase (26.3%) and whiff (17.7%) rates. However, his ability to fill the strike zone and generate weak contact on his key pitches proved to be key to success, especially with a diverse seven-pitch mix.

This season, his second in Kansas City, he has kept the same formula, albeit with more efficiency.

Kolek has gotten rid of the curveball and improved his overall TJ Stuff+ and ability to limit hard-contact, while maintaining solid zone rates. That has resulted in his posting a 2.77 ERA and 0.85 WHIP over 26 IP with the Royals this season.

The four-seamer has seemed to be key to his success this year.

The TJ Stuff+ difference isn't all that great, but it is better in 2026 (91) than it was in 2025 (90). However, the biggest improvement in the pitch is that he's throwing it in the strike zone more (60.9% to 52.5% in 2025) and generating more chases (33.3% to 17.1% in 2025). It has become more of a vertical offering in 2026, as the iVB went from 12.9 last year to 13.3 this year, and his HB on the pitch went from 8.2 to 6.7. It is also generating more spin, as its 2,243 RPM is higher than the four-seamer's 2,176 RPM in 2025. 

Below is a clip compilation of Kolek's four-seamer with the Padres back in May of 2025 and his four-seamer this year against the Cardinals. Both produce whiffs up in the zone, but there is much better velocity and vertical movement on the 2026 four-seamer than the 2025 version. 

Even though it's not an elite pitch based on TJ Stuff+, the four-seamer has shown enough improvement and effectiveness to be not just a solid offering but also to set up the other five pitches in his repertoire. The growth of Kolek's four-seamer is another success story for this pitching-coaching team, especially for assistant pitching coach Mike McFerrin, who primarily works with pitchers to improve the shape of their pitches. 

What Will Kolek's Outlook for the Remainder of 2026 Be?

Kolek was called up to replace Cole Ragans, who landed on the IL due to left elbow impingement. That said, Ragans made a rehab start on Saturday against St. Paul, and he looked good overall, with solid TJ Stuff+ and chase numbers, in addition to three strikeouts and just three hits and one run allowed in 4.1 IP. 

Based on this rehab outing, it's likely that Ragans will return to the rotation soon. However, even if Ragans returns, Kolek will not lose his place in the rotation. With Kris Bubic also on the IL, Kolek will have more time as a starter, but when Bubic is ready to come off the IL as well, the Royals will have a dilemma on their hands.

First off, even when Bubic returns, Kolek needs to remain in Kansas City. He has proven that he is a valuable member of this pitching staff, regardless of role. That said, he has proven that he may deserve a regular spot in the rotation, even with Ragans and Bubic healthy (as Jack Johnson of Locked On Royals stated on Twitter).

Noah Cameron has looked better recently and produced a quality start in his last outing on Friday against Seattle. Unfortunately, he didn't get any run support and, as a result, got the no-decision. Still, his TJ Stuff+ summary from Friday's game looked solid and demonstrated that Cameron may be on the upswing after a slow start.

Thus, the Royals may be forced to move Bubic back to the bullpen, a role he hasn't had since 2024. While Bubic has been serviceable as a starter this year, he hasn't been as dominant as he was in 2025, when he made his first All-Star team. His ERA is 4.11, his WHIP is 1.23, and his FIP is 3.77 in 50.1 IP. That said, while those are solid numbers, the zone, chase, and xwOBACON have been average to slightly below this year, as illustrated in his TJ Stuff+ summary below.

Would the Royals be better off moving Bubic to the bullpen? That would allow him to not just stabilize the bullpen a bit (it's unlikely Carlos Estevez returns to 2025 form or at all), but allow his stuff to play up more. Furthermore, that would also preserve his health, which is something he's struggled with in the past (he had Tommy John surgery in 2023). 

Then again, that may be too bold a move, especially with Ragans' own checkered injury history. If Ragans goes down, they will need Bubic in the rotation again. 

Regardless, the decision isn't IF Kolek will be in Kansas City. It will be whether he is in the rotation or the bullpen after Ragans and Bubic return from the IL. 

That's a good place for the Royals to be, especially considering how hard their pitching depth has been hit early in the year.