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The Padres reliever that is striking out everybody

Jose Castillo is striking out batters at a higher rate than anyone has to start a career.

Cincinnati Reds v San Diego Padres Photo by Denis Poroy/Getty Images

A few weeks ago, most baseball fans probably didn’t recognize the name Jose Castillo. A lot probably still don’t. To cut it short and get to the reason why he’s worth writing about is he’s faced 14 batters in his short major league career, striking out nine of them and walking none. Writing about a four inning sample size may seem dumb, but his start does have plenty of historical significance.

I took every rookie in the history of baseball with at least four innings pitched and ranked them by K-BB%. Castillo ranked first out of a 5,383 sample size.

Top 20 K-BB% among rookies in baseball history

Name Team IP K-BB%
Name Team IP K-BB%
Jose Castillo Padres 4 64.3
John D'Acquisto Giants 4.2 60
Joe Musgrove Astros 4.1 46.7
Michael Wacha Cardinals 10.2 40.5
John Holdzkom Pirates 9 37.5
Edward Paredes Dodgers 12 36.4
Rick Ankiel Cardinals 7 36
Jon Garland White Sox 4 35.7
Rafael Martin Nationals 16 35.3
Mo Sanford Rockies 6.1 34.6
Brandon Woodruff Brewers 7.2 34.5
Paul Lindblad Athletics 7.1 34.3
Edwin Diaz Mariners 51.2 33.6
Sonny Gray Athletics 4 33.3
Bartolo Colon Indians 5 33.3
Josh Hader Brewers 85.2 32.5
Seranthony Dominguez Phillies 19 32.3
Francisco Liriano Twins 24.1 32
Yhonathan Barrios Brewers 6.2 31.8
Minimum 4 IP FanGraphs

To understand Castillo a bit more, let’s learn about his history. A 22-year-old that hails from Valencia, Venezuela, he was signed by the Rays in 2012. After seeing limited time as a starter and a reliever in the lower minors with mixed results. He was then shipped with Wil Myers and Ryan Hanigan to the Padres in 2014, a deal that brought the Rays most notably Jake Bauers. In his first year with the Padres organization, they worked him as a starter between two levels. He put up a 3.74 ERA in 79.1 innings, but limited the excitement by owning a 5.8 K/9 and 3.6 BB/9. The Padres didn’t like the ceiling for him as a starter, so he was sent to the bullpen, where he’s remained for the past three seasons.

Moving to the bullpen significantly upped the outlook for Castillo, as his profile as a pitcher has extremely changed.

Jose Castillo SP vs RP in minor league career

Role K% BB% K-BB%
Role K% BB% K-BB%
Starter 17.7% 9.4% 8.3%
Reliever 27.5% 7.0% 20.5%

Jumping to a more recent view, he’s been dominant at every level he’s played this year. In 15 innings at Double-A this year, he posted a 3.00 ERA and 1.76 FIP, striking out over 15 batters per nine. That was more than enough to get him a promotion to Triple-A, where he posted a 1.08 ERA and 3.56 FIP in 8.1 innings, striking out over nine batters per nine.

And it isn’t just the early results that are exciting for Castillo. He’s described as having a lively repertoire and a lefty possessing movement on both his fastball and slider.

“Jose Castillo snuck up on me a little bit as 2017 wore on; saw him a few times early in the year and put him in the back of my mind before really bearing down on him late in the year when he more consistently started flirting with an upper-90s fastball. The San Diego Padres protected him on their 40-man roster over the winter, indicating they’re clearly interested in figuring out if he can help the big league bullpen fairly soon; feels like there’s a natural fit here as a situational left-handed reliever with perhaps a chance at more general high-leverage set-up work assuming better command and consistency. Big-bodied kid with some baby fat still on him; naturally strong just by virtue of his build, but not necessarily well conditioned at this point; perhaps some modest room to add strength here in subtle ways that could help him consistently work in the upper 90s. Just turned 22 years old two weeks ago, so well ahead of schedule now with clearly some room left to grow into his body, as well as his career path.”

The pitch usage in these four innings has been a bit interesting. He only throws a fastball and a slider, actually throwing the slider more than the fastball. Out of 434 pitchers this year that throw a slider, there’s only 29 pitchers that do that, so it is somewhat rare. Castillo’s usage differential (slider% subtracted from fastball%) is the 20th lowest out of that same exact group.

Fastball and slider usage differences

Name Team IP FB% SL% Differential
Name Team IP FB% SL% Differential
Sergio Romo Rays 26 32.1 57 -24.9
Pat Venditte Dodgers 4.1 36.2 61 -24.8
Edubray Ramos Phillies 24 37 58 -21
Bryan Shaw Rockies 33 0.2 19.2 -19
Justin Anderson Angels 22.1 40.6 59.1 -18.5
CC Sabathia Yankees 63.1 17.1 34.5 -17.4
Adam Ottavino Rockies 28.1 36.6 52.2 -15.6
Tyler Lyons Cardinals 13.2 41.6 56.6 -15
Andrew Kittredge Rays 16.2 41.6 54.8 -13.2
Dellin Betances Yankees 30 43.5 56.5 -13
Andrew Miller Indians 14.1 44.5 55.5 -11
Vidal Nuno Rays 13.1 19.2 29.8 -10.6
Victor Arano Phillies 21.1 42.1 52.6 -10.5
Brad Hand Padres 35.1 45.3 54.7 -9.4
Masahiro Tanaka Yankees 72.2 26.4 35.2 -8.8
Adam Warren Yankees 10.2 38.9 47.4 -8.5
Adam Morgan Phillies 18 33 41.4 -8.4
Josh Lucas Athletics 9.1 46.9 53.1 -6.2
Greg Holland Cardinals 13.1 44.2 50.2 -6
Jose Castillo Padres 4 48.3 51.7 -3.4
Minimum 4 IP FanGraphs

The pitch that seems to be doing most of the work for him is the slider. On the 18 he’s thrown this year, nine have been whiffs. That 50% rate is tops in baseball.

Top 10 SwStr% with sliders

Player Name SwStr%
Player Name SwStr%
Jose Castillo 50
Scott Copeland 40
Reymin Guduan 38.5
Odrisamer Despaigne 36.4
Ryan Tepera 36.4
Dennis Santana 36
Ryan Pressly 35.3
Scott Alexander 34.4
Dominic Leone 33.3
Tanner Scott 32.2
Minimum 10 pitches FanGraphs

The movement he gets on it is decent.

Slider movement
Baseball Savant

It is a small sample size and all, but the Padres have themselves a reliever that is showing insane results, has shown plus-control skills, has a fastball that sits mid-to-upper 90s, and a slider that nobody is picking up on.

It’ll be impossible for Castillo to keep up this K-rate, but he may just have had a better first four innings to a major league career than any pitcher ever has.

*All numbers and graphs are as of June 14th