A year ago, young right-hander Rayner Castillo was one of the fastest rising players in the system. In 2025, he spun his wheels at the High-A level, suffering from some uncharacteristic wildness and more erratic velocity. He continued to rack up ground balls, but the contact got louder and the whiffs dried up a bit. It wasn’t until late in the season when he finally put it together and started shutting teams down again. That’s just a minor setback for a 21-year-old pitcher in his first look at the High-A level, but Castillo needs
to get back on horse and make progress in 2026.
Castillo was a member of the Tigers’ 2021 international free agent class out of the Dominican Republic. He was just 16 at the time, and a fairly lean, undistinguished right-hander. It took him a few years to find himself as a pitcher, but advanced strike throwing got him to the Complex League for his age 18 and 19 seasons. He finally broke into full season ball after a great Complex League showing in 2024, now 6’3” and with plenty of muscle added to him frame. The strikeouts were lacking, but Castillo was throwing a very easy 95-96 mph sinker with advanced command and getting a ton of outs on the ground. His slider flashed plus and he had the makings of a solid changeup but both were very inconsistent. Progress with his secondary pitches, especially the changeup, was the main prescription for progress in 2025.
However, we didn’t get that progress. Instead, Castillo’s easy, balanced delivery wasn’t producing quite the same velocity and he sat around 93-94 mph most of the 2025 season at High-A West Michigan. Work to tune up the movement on his slider and changeup combo led to a little more wildness than we’ve seen before from him, and he really struggled to shut down opponents with runners on base. It wasn’t until August and September that he really dialed things in and finished strong.
So, to put a positive spin on it, Castillo got a lot of experience navigating better lineups with less than his best stuff, but finished the year looking back in form. An off year is natural at his age as he stretched out to 98 2/3 innings of work. But clearly there is plenty of work ahead if he’s going to break through at the Double-A level in 2026.
Castillo’s slider is typically 83-84 mph, and in 2024 he was already showing some feel for adding depth or sweep depending on the hitter and the situation. At the same time, he would still occasionally spike one pretty badly, and we were looking for more consistency as he continued to refine the pitch. That didn’t happen until late in the 2025 season. He was less prone to completely yanking it in the dirt, but it was slower and more rounded off than sharp during the summer months, and he continued to have it back up on him at times. Most of his helium coming into the season was on the basis of his easy command of the sinker at 95-96 mph and up to 98 mph, backed by a pretty sharp slider. He lost both for long stretches in 2025, and really only in his final starts in August and September did the two pitches come back to form consistently.
Castillo’s changeup didn’t show any real signs of improvement either, and developing that third pitch was a big goal for 2025. He was throwing a circle changeup in 2024, and while he appeared to tinker with a few different variations this season, he never really got it locked in. It’s still too firm, and with the sinker diminished for much of the summer, the velocity separation was pretty poor.
So, by season’s end, we basically had the same Castillo we saw in 2024. He got back to sitting 95-96 mph with pretty easy command of the sinker. The slider got sharper and he started picking up more whiffs again. But the changeup didn’t improve much if at all. The hope is that this was just a year of growing pains. When a young pitcher makes the leap Castillo did in 2024, there’s often a period of inconsistency as they work on things and try to take the next step.
We’re going to ride with Castillo again and not drop him down in the rankings or grade for now. He won’t be 22 until June, and as long as he has the velo and the slider back this season, he should do well and advance to Double-A Erie. He’s unlikely to ever be a big-time strikeout artist, and the hard sinker and his durability and typically good strike throwing remains the foundation of his approach to hitters, but a depth starter projection is still viable. More likely, he’s a future relief option, but he’ll still have to show better command of the fastball and the slider to get there.
