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In tonight's Raymblings I'm going to compare a current major league pitcher for the Rays to a current minor league prospect of the Rays. Diego Castillo is a RHP prospect currently pitching in the AFL, and his stuff looks pretty similar to Rays ace Chris Archer--at least close enough to take a deeper look.
| Usage (%) | H mov (in.) | V Mov (in.) | Velocity (mph) | |
| Archer Fastball | 48.45 | -3.35 | 10.15 | 95.17 |
| Archer Slider | 40.22 | 3.04 | 0.61 | 88.99 |
| Archer Change | 11.29 | -7.18 | 3.84 | 87.57 |
| Castillo Fastball | 58.57 | -6.38 | 7.43 | 99.17 |
| Castillo Slider | 32.86 | 2.08 | 0.65 | 88.73 |
| Castillo Change | 8.57 | -6.34 | 5.67 | 91.38 |
| Average MLB FB | -4.2 | 8.9 | 92.4 | |
| Average Slider | 2.8 | 1.2 | 84.3 | |
| Average Change | -6.7 | 4.1 | 83.7 |
They use the same pitches, and even have similar usage rates. Castillo has much more velocity on the heater and change up than Archer, and both are well above major league average velo with all three pitches. Castillo is currently working in a bullpen role, so he might have an extra tick or two on his pitches due to that.
Castillo's pitch movement doesn't appear to be as elite as his velocity. The fastball run is good, but the lift is well below average for a fourseam. This not only hurts the fastball, it also factors into his other pitches. Where Archer has 10" of vertical movement separation from fastball to slider, and 6" to his change up, Castillo has only 7" to the slider and a mere 2" to the change up. The change up also has identical run to the fastball, which is probably not good.
Castillo's slider, meanwhile, is his best pitch. I say this confidently because it is so very close to being Archer's slider, which is industry-wide considered to be one of the best sliders in baseball, if not the best. The velocity and drop are both the same, and Castillo is missing only 1" of run on his slider compared to Archer's. They both throw the slider close to league-average movement, but with 4.5 more ticks on the gun. Archer has excellent command of his slider, something Castillo will want to work towards to get the most out of the pitch.
Now that I've made the case that these pitchers are at least fairly similar, let's look at how they performed along similar stops in their minor league career.
| Castillo Age | Level | Innings | K/9 | BB/9 | H/9 | HR/9 |
| 20 | DSL | 25 | 9.4 | 4 | 9.4 | 0 |
| 21 | A- & A | 32.2 | 7.7 | 3 | 7.4 | 0.3 |
| 22 | A & A+ | 60.1 | 10 | 2.5 | 9.2 | 0.6 |
| Archer Age | Level | Innings | K/9 | BB/9 | H/9 | HR/9 |
| 18 | Rookie | 56.2 | 8.4 | 3.8 | 9.7 | 0.6 |
| 19 | A | 115.1 | 8.3 | 6.6 | 7.2 | 0.6 |
| 20 | A | 109 | 9.8 | 5.4 | 6.4 | 0 |
| 21 | A+ & AA | 142.1 | 9.4 | 4.1 | 6.4 | 0.4 |
| 22 | AA & AAA | 147.1 | 7.9 | 5.3 | 9 | 0.7 |
There are a few big differences we can see right off the bat. Archer was pitching in more advanced leagues when he was Castillo's age, and he was also starting games and racking up many more innings. On the other hand, Castillo walks fewer batters, suggesting he has better command of his pitches than Archer.
I don't know if the plan is to convert Castillo to a starter or not. If they think he can be something like a Chris Archer with better command, that would certainly be worth the wait as he builds up innings in the minors. If they think he is a bullpen version of Chris Archer, Castillo is on pace to provide that to the major league club as early as next September, though 2018 seems more likely. These are exciting options to consider for this young man.