Castro's strong performance during Cactus League performance earned him a greater role in Arizona's bullpen out of spring training. The 28-year-old mostly handled setup duties, but he got some run as the D'Backs' closer early in the season. The right-hander compiled 5 saves, 3 wins and 8 holds by the end of May to go along with a 2.22 ERA and 0.99 WHIP. It looked like a breakout season was on the horizon, but Castro opened June with a couple of rough outings and was soon ousted as closer. The right-hander still had a solid season overall, as his 6 wins, 7 saves, 13 holds and 1.18 WHIP were all personal bests. Castro ended 2023 on a high note with a 14-game scoreless streak with 17 strikeouts over 12.2 innings. Look for him to spend most of 2024 in the 6th, 7th and 8th innings. Read Past Outlooks