Why Diego Castillo could become a high leverage arm again in 2023
Diego Castillo had a bit of a down year in 2022, but there are reasons to hope for a bounce back. Let's take a look at the veteran reliever and what he is likely to bring to the bullpen in 2023.
Diego Castillo has been a somewhat frustrating player since being acquired from the Tampa Bay Rays in July of 2021. His performance has been wildly inconsistent, but Castillo has the ability to regain form. I believe we will see an improved version of the reliever in 2023.
It was fair to wonder why the Tampa Bay Rays moved on from Castillo in the first place. There were questions about Castillo’s shoulder and his lack of conditioning over his time with the Rays, and many speculated this was a factor in the team moving on from him.
At the time of the trade, he was coming off a career year with Tampa in 2020 and was putting together a solid 2021 campaign. Typically the Rays will move on from players early, shipping Castillo to Seattle with two and a half years of club control remaining.
The 29 year old reliever performed adequately in 2022, but dealt with some injuries and poor performance throughout the season. He ended up posting a 3.64 ERA and a 3.68 FIP over 54.1 innings.
These numbers were down a fair amount from his previous season, but his expected numbers were still very impressive. According to Baseball Savant Castillo ranked in the 80th percentile or above in xBA, xSLG, and xERA. He also ranked in the 95th percentile in Hard Hit %, which means he limited hard contact fairly well.
These expected results and advanced metrics seem to indicate that Castillo was actually very good, and his actual results may not reflect how good he was. These numbers mirror his 2020 and 2021 seasons, in which he was very productive.
There was one big difference in Castillo’s production last season, the Dominican native struggled to miss bats. He ranked in the 59th percentile of Whiff %, and K%, which is down significantly from 2021.
In addition to his struggles to miss bats, the right hander also walked hitters far too often. His walks per nine innings skyrocketed to 3.64/9 while his strikeouts dropped below one per inning.
Missing fewer bats and walking more batters is typically not a recipe for success, but why did this happen?
Castillo’s slider was much less effective, flattening out a ton over the course of the 2022 season. He struggled to command the pitch, and the break seemed inconsistent all season.
His slider generated 40% whiffs in 2021, a number that fell all the way to 32% in 2022. He needs this pitch to miss bats again if he wants to get back to high leverage form, and he has to find the strike zone more often.
The “Dominican Big Boss” will also be competing with a new rule this year, the pitch clock. Pitchers will have 15 seconds to deliver a pitch with no runners on base, and 20 seconds with men on.
Castillo had the second highest time between pitches of any player in the Mariners bullpen last season, just behind Paul Sewald. This will be a huge adjustment for Castillo to make, but if they can get his tempo up and get him pounding the zone he could have a big year.
The good news about this is that Seattle excels at helping relievers fine tune their offerings. I believe with more consistency to the shape of his slider and pounding the strike zone can get Castillo to become a back end bullpen arm once again.