Royals’ Spring Breakout standout might be primed for 2026 MLB call-up

It feels like there is rarely any such thing as a relief pitching prospect. Usually, the guys handed the ball in high-leverage situations are former starters who did not have the length to stick in a rotation, or unheralded arms who capitalized on an opening ahead of them.

Current Kansas City Royals closer Carlos Estévez started his minor-league career as a starting pitcher in the Colorado Rockies organization before racking up 99 saves over the last three seasons. He was not a highly sought-after prospect for the Rockies, but he has proven his value over and over again.

His story is the story of many bullpen arms around the league, and that is what makes finding the next gem so hard to project. I thought Dylan Coleman was going to be the next steady reliever for the Royals, but Coleman is now scuffling to keep his MLB dream alive in the New York Yankees organization.

So many of these players come out of nowhere, while others have the stuff the public loves only to fold when the opportunity arrives. That makes projecting the next impact reliever a tough exercise. But the Royals may have a pretty clean outlook for right-handed pitcher Dennis Colleran after his strong spring.

The Royals may have a burgeoning relief prospect in Dennis Colleran after a spring surge

Colleran was a raw project when the Royals drafted him in the seventh round of the 2024 MLB Draft, and he quickly proved his worth in his first professional season.

The Massachusetts native pitched in 44 games in 2025 between Low-A Columbia, High-A Quad Cities, and Double-A Northwest Arkansas, posting a 9-0 record with a 2.85 ERA in 66.1 innings. The Northeastern alum was solid in both the strikeout and walk departments as well, carrying a 27.1% strikeout rate against a 12.8% walk rate. The Royals wanted to see more of Colleran in the fall, and he made a name for himself in the Arizona Fall League.

Pitching for the Surprise Saguaros, Colleran kept the momentum rolling, allowing only one run and two hits in 7.2 innings. In that span, he struck out 11 batters while walking only three. It was more of the same for Colleran, capping off his season in dominant fashion.

Prospect Savant scored him as one of the league’s best pitchers, thanks to a 94th percentile wOBA allowed and a 93rd percentile fastball velocity at 99.5 mph. The 22-year-old was firmly on prospect radars by then, which is no small feat for a relief-only profile.

It would have been easy for Colleran to ride that wave into a slow spring, but the Royals rewarded him with an invite to camp and the righty delivered. Most of his competition was minor-league quality, but that should not erase the fact that he allowed only one hit and no walks in four innings of work while striking out three. He faced the minimum, with 12 up and 12 down in Cactus League action.

The Royals gave Colleran a good run in big-league camp, not reassigning him until March 14. He was always going to be an extreme long shot to make the Opening Day roster, but he still spent meaningful time around the major-league group and coaching staff, and that counts for something.

Starting the season at Triple-A might be aggressive, but it would not be out of the question if Kansas City feels confident in his ability to help the team sooner rather than later.

Colleran’s profile gets even more intriguing when you consider that he scrapped an average slider for a plus sweeper, which he showed off this spring. He posted a 38.9% CSW on that pitch alone, with some solid grouping at the top of the zone early in counts. While he had some erratic pitches early in camp, fans could see more of his stuff landing in the zone as spring progressed if they followed his Baseball Savant pitch log.

One pitch can define a select few pitchers, but it matters for Colleran to have another offering he can trust outside of the cutter and four-seam fastball. Overall, hitters swung and missed 40.9% of the time against him this spring, an absurd number that helps back up the perceived quality of his stuff.

It also feels like Colleran is getting extra chances that some arms would not, namely his appearance in the final inning of the Spring Breakout against the Texas Rangers. Colleran was slightly older than the average Rangers prospect, but he still needed only nine pitches to close out the game, including a 100.2 mph fastball and one strikeout.

That is probably the last some casual Royals fans will see of Colleran for a while, but on his current trajectory, he may not be gone long.

Some things would have to break a certain way for Colleran to make his way to Kansas City before the season ends, but crazier things have happened with this organization.

The Royals head into Opening Day carrying a large group of right-handed relievers with no options and, because of that, only so much leash. Kansas City will certainly give players like Nick Mears, John Schreiber, and Alex Lange the benefit of the doubt in 2026, but if any of them stumble, Colleran’s chances of reaching the big-league roster only go up. And that only accounts for underperformance, not the ever-present likelihood of injury in a bullpen.

Colleran still has to hold up his end of the bargain and build on the calendar year of success he has already put together. But the path through the minor-league forest is there, and the hard-throwing righty could absolutely be wearing a Royals jersey again before the season ends.