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Rays Top 50 Prospects: No. 26, Diego Castillo

MLB: Spring Training-Boston Red Sox at Tampa Bay Rays Kim Klement-USA TODAY Sports

One of the many electric arms the Rays will call on in 2018 to provide strength out of the pen, this prospect received a small international signing bonus and is earning every penny - and then some.

No.26, RHP Diego Castillo, 24 yrs old

Born: Jan 18th, 1994 in Cabrera, DR

Height/Weight: 6’3” 240 lbs Bats/Throws: R/R

Signed: by the Rays as an international free agent in 2014 for $64,000

Twitter handle: NA

Twitter profile statement: NA

Baseball America Rankings

  • Ranked 29th best Rays prospect post 2017

DRB Writers ranking

  • High: 21st
  • Low: 35th
Minor League Baseball: Arizona Fall League-Fall Stars Game Mark J. Rebilas-USA TODAY Sports

Diego Castillo: Abilities

  • Fastball that hits the upper 90s, often with sink
  • Plus slider
  • Worked multiple innings often for the first time in 2017

Scouting grades ‘18 (Pipeline): FB: 70 | SL: 55 | Ctl: 50 | Overall: 45

  • Abilities notes: Castillo also can throw an occasional change-up, but it isn’t a large part of his arsenal. His control has been steadily improving as he’s approached the majors.

Joined the Rays by way of....

The international draft as mentioned above, in 2014. The Rays aggressively moved him up from the DSL in 2014 (where he was team mates with LHP Genesis Cabrera) to Hudson Valley in 2015, where he performed so well (2.31 ERA, 1.11 Whip and 4 saves) that he was promoted to Bowling Green (LoA) before the season ended.

He’s worked on two teams yearly ever since.

Latest Transaction: Rays selected the contract of Castillo from Durham Bulls Nov 20th, 2017.

Note - I’ll be disappointed if he doesn’t begin the year with the Rays, but with so many options someone deserving will have to begin in AAA. Whether he does or not, he’ll likely be there before too long with the reported 4-man rotation placing more emphasis on keeping the pen well stocked with ready-to-go arms.

Facts, Honors, and Awards

  • Named a rising star after playing for Peroia in the AFL in 2016
  • Added to the 40-man roster in November 2017,
  • Fangraphs ranked Castillo 18th among Rays prospects pre-2017 and added this,

He was 96-100 with his fastball in the Arizona Fall League with a short but sharp upper-80s slider in the 84-88 mph range. He also throws a low-90s changeup, which is below average.

RHP Diego Castillo continues to impress, retiring Boston A-teamers Andrew Benintendi, Hanley Ramirez and Rafael Devers in order


Diego Castillo 2017

GP 51
GP 51
GS 1
IP 71.2
W 4
L 5
Sv (SvO) 15 (18)
H 58
BB 20
SO 90
HR 3
AvgA 0.214
Whip 1.090
BAbip 0.309
LOB% 71.6%
GB% 49.5%
FB% 27.2%

Stats Notes: Diego works with his heavy fastball and rarely gives up any HRs, (only three allowed in 2017.) If that continues going forward, it could be one of many assets that give him a shot to close at some point.

Interesting Comparison: Nate Jones

Although Nate has an inch or two on Diego, they are both big right-handed relievers that have similar stuff. Each uses a fastball-slider combination and depend on high velocity to go after hitters. Jones has been known to average his fastball velocity at approximately 98 MPH, which is about where we expect to see Castillo.

Both are also known to generate a healthy number of ground balls, as indicated by Jones and his career 47.4 % GB rate and similar rates for Castillo throughout his minors career. Meanwhile, Jones has also maintained K/9 above 10 through most of his time in MLB and we’d expect Castillo to achieve that as well.

Jones has been a solid 7th or 8th inning reliever for the White Sox when healthy and was often noted as a closing option. Health and other options have gotten in the way of that over time, but there’s little doubt that he is one of the tougher RHP relievers to face in the AL.

There’s a good chance that Castillo begins in that role, and just like Jones his name could be on the list of potential closers in short order.

Notes for 2018 and beyond

Unlike Jaime Schultz, who we just profiled at No 27, Castillo has been working in relief since he was signed by the Rays. He’s been developing his craft, learning the ropes, and has developed significantly over the last two seasons.

In 2016, Castillo put together an impressive season while in LoA with a 2.03 ERA and 1.13 whip, earning 7 saves in 9 attempts in the process. However, he struggled some when promoted to HiA and allowed 28 hits and 6 walks through 20 innings, resulting in a 1.67 whip.

But it’s the steps he took forward in 2017 that show us that he’s ready to be tested in MLB. He held hitters in AA and AAA to a .216 average combined and held a 1.09 whip while also earning the save in 15 of 18 opportunities. In the second half of the season, all in AAA, he managed 36 SO in 23.2 innings and a .198 average against, going 6 for 6 in save opportunities.

If there’s one thing to look for with Castillo is his work with RISP. Although it’s a small sample size (as most things are with relievers), it seems to be one area where Castillo gets into trouble and allows more hits than usual (.255 average against in AAA and .259 in AA for 2017). That may be linked to overthrowing in those situations or a number of other issues, but it’s something to look for going forward.

Still, those are things he can continue to work on as he performs at a very high level in the majors.

In short, Castillo seems ready to begin the season with the Rays and could very quickly become one of the favoured options at the back of the pen. As one of the better options to take over from Alex Colome one day, he’ll be a lot of fun to watch.

Diego Castillo: Spotlight Videos

Recap and links of previously listed DRB Top 50 Rays Prospects

*Note: rankings were adjusted and reflect recent additions to the system - it is now a Top 55 list