Breaking down Seattle Mariners starter, Luis Castillo

After having an easier week when it comes to facing top level starting pitching, the St. Louis Cardinals are being thrown right back into the fire this week. They got lucky as they avoided Arizona Diamondbacks ace Zac Gallen, who pitched Sunday. However, the same cannot be said for the weekend series against the Seattle Mariners as they will be facing off against budding ace George Kirby and one of the game's best in Luis Castillo. Castillo is off to a torrid start pitching to a 0.73 ERA across 24 ⅔ innings whilst striking out 26 and allowing just 4 walks. Down below we are going to see what has enabled the former Cincinnati Red to become one of the early season front runners for the AL CY Young.

Will include batted ball profiles next week. Unfortunately, there is not enough data in that category yet to have it support any claims.

Pitch #1 - Four seamer - 2023 usage rate - 42.9 percent

2023 stats - Average velo - 95.1 MPH - Spin rate - 2,342 RPM - vertical movement - 15.6 inches - horizontal movement - 11.5 inches

Honestly, I’m a little surprised Castillo’s usage on his four seamer is this high. Traditionally when you think of him as a pitcher you immediately go to his sinker and changeup. Despite that though, in terms of the expected metrics, it’s actually been his best pitch over the past two seasons. There have only been 11 batted ball events against it this year, but it’s allowed an xBA of .083, xSLG of .175 and xWOBA of .176. Importantly as well as the numbers last season back it up as in those areas the numbers were .180, .281 and .247 respectively. Additionally, his four seamer produces swing and misses. The whiff rate on the pitch this season is 39.2 percent, 5.5 percent higher than last season’s mark. When thrown in the zone the whiff percentage on it the last two seasons have been 30.4 percent and 32.2 percent. Despite having a lineup filled with elite fastball hitters this is a pitch we will see Castillo throw a lot, fearlessly.

Pitch #2 - Sinker - 2023 usage rate - 21.7 percent

2023 stats - Average velo - 95.1 MPH - Spin rate - 2,104 RPM - vertical movement - 25 inches - horizontal movement - 18.8 inches

When looking at the expected metrics this grades out as Castillo’s worst pitch. The xBA on it last season in 130 batted ball events was .272 with an xWOBA of .330. Notably, despite being thrown 229 times fewer than his four-seamer last year, hitters put it in play 130 times the most amongst his pitches and 45 times more than the four seamer. Traditionally when Castillo throws his sinker it is thrown in the strike zone. Not including this year, since the start of the 2017 it has led his arsenal in thrown in the strike zone percentage in every season including 56 percent last season.

Pitch #3 - Slider - 2023 usage rate - 19.5 percent

2023 stats - Average velo - 85.5 MPH - Spin rate - 2,306 RPM - vertical movement - 35.5 inches - horizontal movement - 1.8 inches

When Castillo throws his slider out of the zone and batters swing, they almost always whiff at it. The chase whiff percentage on his slider was 68 percent last year, the second highest mark of his career in a season. Over the past two seasons the launch angle against it was 9 degrees last season and 12 this year, the second highest number in each of the past two seasons. This season aside hitters have typically struggled to make solid contact against the slider. The hard-hit percentage against it last season was 28.9 percent, the lowest amongst his pitches.

Pitch #4 - Changeup - 2023 usage rate - 15.9 percent

2023 stats - Average velo - 87.9 MPH - Spin rate - 1,953 RPM - vertical movement - 34.7 inches - horizontal movement -17.9 inches

Even though the expected metrics say his four seamer is his best pitch, I still think Castillo’s best offering is his famous changeup. Outside of last season, where his slider was the leader, it’s produced the highest chase rate for him in every season since 2017. In 2019, ‘20, ‘21 and thus far this season it also has his lowest hard-hit percentage. When Castillo throws it traditionally it is out of the zone as in every year since ‘17 it has the highest out of zone percentage amongst all of his pitches. Lefties see this pitch a lot more than righties as last season the pitch percentage against left-handed batters was 29.4 percent, against righties it was 15.1. This season it is 23.8 and 7.1 percent respectively. The likes of Tommy Edman and Brendan Donovan should see this pitch quite often against Castillo.

Key matchup - Brendan Donovan - It is weird to highlight the key matchup in a game and not have it be one of Nolan Arenado or Paul Goldschmidt, but this does feel like one of those weeks. If there is any type of crack in Castillo’s armor, it is how he performs against lefties. Over the course of his career his OPS against left-handed hitters is .716, which is significantly higher than the .617 he allows to righties. Additionally, despite only having 24 more total plate appearances against lefties he has walked 66 more left-handed batters than right-handed ones, whilst allowing 12 more homers to lefties. So, if the Cards are going to push runs across the board against Castillo, it is going to start with lefties, and Donovan, their leadoff man fits that profile perfectly. Last season, his run value per 100 four seamers faced was 0.8, against sinkers it was 0.4, sliders it was 0.9 and changeups it was 2.2. Donovan does not struggle against any of Castillo’s pitch types so there is a more than solid chance he is able to get himself on base once or twice for the big bats behind him.

Prediction - Castillo throws 7 innings, allows 1 earned run and strikes out 7.