Castro (3-4) took the loss in Monday's 7-5 defeat at the hands of San Francisco, allowing two runs on two hits with two strikeouts in 1.1 innings.
Castro relieved Rich Hill with two on and two out in the fourth and induced a Tommy La Stella lineout to escape the threat, but he surrendered a Kris Bryant two-run home run in the fifth to fall in line for the loss. The earned runs were the first in August so far for Castro, who now has 3.38 ERA, 1.30 WHIP and 56:29 K:BB in 50.2 innings this season.