Diamondbacks 2023 Player Reviews: Miguel Castro

Miguel Castro signed with the Diamondbacks early in the 2022 offseason. The hard-throwing right-handed reliever with a devastating pitch arsenal was brought on to provide a much-needed boost to the 2023 bullpen. 

It wasn't a perfect season for Castro, but for a large portion of 2023 he performed excellently. He began his Diamondbacks career with back to back solid months, allowing just six runs over the course of 26 appearances in April and May. Through these early months, he sported a 2.22 ERA and 0.99 WHIP. Opponents were hitting just .182 against him.

With the lack of a defined closer role in Arizona's bullpen and a revolving door of late relievers vying for the position, Castro's 22 strikeouts and high-velocity sinker made him a candidate for the job. Manager Torey Lovullo began to turn closing duties over to Castro, who was 4-for-5 in saves at the end of May.

June, however, is when things began to break down for the right-hander. After picking up a tough-fought save in the first game of a series against the NL-leading Atlanta Braves, Castro was given the ball with a 5-4 lead again the next day. With two outs and bases loaded, Castro served up a middle-middle sinker to Braves outfielder Eddie Rosario, who blasted a go-ahead grand slam and secured the win for Atlanta.

Castro struggled in June, giving up runs in three consecutive appearances. He had a monthly ERA of 6.00 in June, allowing six runs in just 9 innings of work. His struggles continued in July and August, as his season ERA gradually climbed to a 5.20 at the end of August, helped along by a brutal 10.45 monthly ERA. He was 2-for-5 in save opportunities over the three-month stretch. 

However, the righty flamethrower came back with a vengeance in September. With a more solidified bullpen aided by the addition of RHP Ryan Thompson and closer Paul Sewald, Castro was able to avoid save situations and excel in a more defined middle-inning role. Castro pitched 10 scoreless innings in 11 appearances in September with an astounding 15/1 K/BB and 0.60 WHIP. Castro's resurgence became an underrated and crucial aspect of the D-backs' final playoff push. 

Once in the playoffs, Castro looked shaky once again. He appeared in eight games, allowing a run in four appearances, including a walk-off home run by Adolis Garcia in Game 1 of the World Series and a three-spot in Game 4. His numbers continued to grow, finishing the playoffs with a dismal 10.50 ERA, 2.00 WHIP and a 4/5 K/BB over six innings. Opponents hit .280 against him in this eight-game stretch, and the dominance that characterized his September was nowhere to be found.

While it's easy to zero in on his struggles, the reliever was dominant at times, and his 2023 season was better than the numbers might show. Of his 75 appearances, Castro was able to collect 61 scoreless outings, with a positive WPA in 59 of them. He finished the season allowing just a .213 opposing batting average and a 60/25 K/BB. His high-velocity, high-movement sinker slider and changeup make him a weapon, and with Arizona's bullpen stabilizing, he has a chance to excel in low-leverage situations. 

2024 Status and Outlook

Castro will likely retain a role in Arizona's bullpen, partially due to the lack of velocity on Arizona's pitching staff. His one-year deal with the Diamondbacks included a $5 million option if the reliever hit 60 appearances. Lovullo was not hesitant to utilize him in later months, allowing him to reach 75 appearances and trigger his 2024 option. However, while he was brought on to provide late-inning power and contend for the closer role, the emergence of Thompson, Ginkel and Sewald to shut down close games will relegate Castro to a lower-leverage role. Unless significant additions are made to the bullpen--which appears unlikely at this point in the off-season--expect Castro to make a decent number of appearances in 2024.