This young right-hander broke out in a big way in 2024, and has a chance to progress quickly in the upper minors this season.
The Detroit Tigers farm system is getting a lot of praise these days. The bigger names are well known, but a less discussed strength of the system is the stockpile of raw but talented arms in the lower levels of the system. They drafted their fair share of prep arms in 2023 and then snagged a really good array of young pitching talent in 2024 as well. The Tigers added a few interesting pitchers in trade last summer, and to top it off they had some pretty intriguing breakouts out of rookie ball last year. Right-hander Rayner Castillo stood out as one of the fastest risers in the entire system.
The big right-hander is still just 20 years old. The Tigers signed him as an international free from Montecristi, Dominican Republic, back in 2021. He’s still listed at 180 pounds, but Castillo was a fairly average framed six-foot-three two years ago. In the interim he’s filled out to at least 220 pounds and now an imposing power pitcher who is consistently throwing some of the smoothest 95-96 mph gas you’ll see in a prospect this young and inexperienced.
Castillo pitches from the wind-up with a simple, minimal leg kick, and has a short arm path which keeps things simple. His relatively short stride for his size does limit his extension a little, but he still showed average major league extension to the plate via his arm length and ability to get out over his front foot into release. The ceiling for his fastball command is quite good because he’s already advanced in that regard and doesn’t have a lot of moving pieces. He tends to be balanced and in control. It’s pretty easy already to envision Castillo as a major league innings eater who is able to get a lot of outs on the ground without much damage.
On the other hand, Castillo doesn’t get that many whiffs off the fastball right now, and while that can improve somewhat, his sinker and fourseamer will probably never be big bat missers. That probably limits his upside a bit. It’s an absolute bowling ball at 96 mph and up to 98 mph already with good depth and tail on the sinker, so he can certainly make it with that as a starter. He’s just not likely to be a dominant power pitcher unless his secondary stuff really comes along in a big way. If he can continue to refine his breaking ball and changeup this season he’ll be on track to move into the upper minors pretty quickly.
Castillo took some time to climb out of the Complex Leagues as a teenager, but after a minor injury in April of 2024, he got better at a rapid pace throughout the rest of the season. These are all small samples, so there’s no reason to really grind over the numbers, but it’s pretty simple. Castillo is pretty hard to hit hard. His fastball command advanced in leaps and bounds this season and hitters could not do much with it at all. It’s really a question of developing his slider and his changeup.
Castillo’s main secondary weapon is an 83 mph slider. He shows some signs of adding sweep to it when he wants to back foot a left-hander, and he can throw a straighter version with more depth to steal strikes in the zone and get right-handers chasing down and away. His overall command of the pitch is still wanting a bit. He got plenty of whiffs in Lakeland, racking up a really nice 42.6 percent whiff rate on the slider, but he’ll still spike or sail a few too many at this point. Nothing unusual for a 20-year-old in Low-A.
The pitch that could really use an upgrade is Castillo’s circle changeup. It has some nice fading action, and the ease at which he can deliver 96-98 mph fastballs gives the changeup some added deception as he maintains his arm speed well. What he needs is more velocity separation. The changeup averaged 90.2 mph this season. In Tiger Town, a place as much spiritual and mental as physical, thoughts quickly turn to a splitter nowadays. Castillo pitched in the Arizona Fall League to get some extra work after missing time early last season, and he did appear to be working on a slower offspeed pitch with more depth there. We’ll have to see if that was work on the circle change or whether they were experimenting with some different grips.
Things did not go well for Castillo in Arizona overall. He made four starts, gave up three home runs, and issued a ton of walks en route to a 7.13 ERA. That lack of control was very uncharacteristic after what we saw in Lakeland, but Castillo was clearly making some adjustments and trying to get comfortable using his slider and changeup more. Both pitches remained a little erratic at times, and he got into some bad counts trying to throw them for strikes. He offered up a few too many hangers as well.
We’re not too concerned about that. He was pretty inexperienced for the level of hitters he was facing, and he was doing the right thing by taking the time to experiment and focus on his weaknesses. Rarely did he give in and resort to just pumping sinkers and fourseamers despite facing far more traffic on the bases than he was used to. He also came up big in a couple of games by spotting the slider well to escape trouble.
There’s a lot of young pitcher to like here. Castillo has plenty of potential as a future starter if he can find an offspeed pitch that works for him and develop it into a consistent weapon. He’ll get another season or two to work on it. If things don’t come along, his advanced fastball combination and slider still give him a very good chance to pitch in a major league bullpen eventually.
2025 Outlook
Castillo is too good for Low-A already, and we’d expect him to start right out in West Michigan this spring. His ability to pound the zone to both sides of the plate and rack up weak contact gives him plenty with which to handle High-A hitters, particularly in a fairly difficult hitting environment in the first place. His slider will play well too as long as he can keep improving its consistency.
The right-hander should be able to build himself up in terms of workload and advance into the upper minor relatively quickly considering that he won’t turn 21 until June. His long-term outlook is strong because the fastball and his delivery give him such a solid floor. Whether he makes it as a starter comes down to holding up to the workload and refining his secondary stuff into consistent weapons that can handle upper level talent and still rack up whiffs. Killing a little more velocity off the changeup is the biggest key there.
After a couple of tough seasons grinding his gears as a teenager in the Complex League, Castillo developed at a really rapid pace in 2024. He filled out his six-foot-three pretty well and can certainly get a little stronger going forward. He should sustain that 96+ as a starter as he builds up toward 100 innings this season. The easy arm speed and relaxed, simple delivery argue in his favor there. There’s a good likelihood that the Tigers have a major league pitcher here eventually, despite his youth and inexperience. His role will be determined by how far he can develop his secondary stuff.