Baseball America says unknown Royals prospect has system’s best fastball

For decades, the fastball has infatuated baseball fans. How many debates in the sports’ earlier years centered around which player had the better fastball? Still, to this day, people are talking about who had the better fastball between Satchel Paige and Bob Feller; that is how long the legs are behind this idea.

Kansas City Royals fans would likely have different answers based on what era they grew up with, or their parameters, but it is still a question that most fans would have some sort of answer for.

Baseball America may not have an answer for which current Royals pitcher has the best fastball, but they have a favorite for the best minor-league pitcher.

Kansas City’s system is light on lights-out pitching talent at the top, but the baseball outlet tabbed right-handed pitcher Dennis Colleran as possessing the Royals’ system’s best heater.

Baseball America tabs Dennis Colleran with the best fastball in Royals farm system

Forgive yourself if you have not heard of Colleran. The Massachussets native did not stray far from home when he attended Boston’s Northeastern University, where he did not post great results as a primary reliever.

He did flash in 2023 with the Worchester Bravehearts of the Futures Collegiate Baseball League
, but even that was only 10 innings. When Kansas City drafted him in the seventh round in the 2024 MLB Draft, it was all about upside for the former top prep pitching prospect.

A lot of that potential rode on Colleran’s fastball, one that Baseball America describes as “a sinker profile fastball but one that averages 95 and has been up to 100.” That workhorse pitch sets up his slider and changeup, and the bullpen arm shot up through the Royals system in his first professional season.

Colleran started out in Low-A Columbia, moved to High-A Quad Cities, and pitched his final game of the season in Double-A Northwest Arkansas. All told, 44 games split between three levels is a healthy debut. Kansas City still wanted to see more and sent him to the Arizona Fall League where Colleran was excellent in his seven appearances.

So, what gives? Why is Colleran not a higher regarded prospect, even if he profiles as a reliever only? Well, Baseball America says his “real control and command questions” limit his floor, but the arm talent has real upside.

Colleran showed that his fall, by striking out 11 of the 28 batters he fcaed while only walking three. His strikeout numbers balanced out his walks in the 2025 season, giving him a respectable 2.12 strikeout-to-walk ratio. Also, while it was only 7.2 innings, Colleran did not look erratic in his Arizona Fall League body of work.

The Royals have also been tinkering with Colleran’s fastball shape. In Arizona, he used three different fastballs with at least a 20% usage of each. Colleran favored a cutter and sinker (using each at least 30%), while tossing a four-seam fastball against lefites primarily. Colleran did work in a slider to play off his cutter, but that was used primarily against right-handed hitters.

Colleran popped in the Arizona Fall League and should be a favorite to start the 2026 season in Northwest Arkansas, with a move to Triple-A Omaha not outside the realm of possibility.

Baseball America previously named Colleran as a favorite 2024 draftee to make their MLB debut in 2025, thanks to his relief-only profile and present stuff. Kansas City is obviously trying to get more from the Northeastern alum and find that ceiling, while bringing the floor up with it.