Before the season, everyone wondered whether Luis Castillo could turn his potential into reality and become the Reds’ next ace. Through two months, that transformation has occurred. Coming into Tuesday’s start against the Indians, the right-hander had a 2.38 ERA, 3.42 FIP, and 3.46 xFIP. His 1.7 fWAR is already closing in on last year’s total (1.9). His 2.8 bWAR ranks 8th among all MLB pitchers. Only Dakota Hudson has a better groundball rate than Castillo (59.8%).
But there’s one area Castillo still needs to work on to truly belong in the elite category: his walk rate. Among all qualified pitchers, only two (Yu Darvish and Aaron Sanchez) have issued a higher rate of free passes than Castillo (11.