Eno Sarris at FanGraphs took a closer look at the Reds' budding rookie. Per Sarris, no one who's thrown at least 200 four-seamers this year has topped Castillo's velocity.
Sarris evaluates that Castillo’s fastball doesn’t have much spin, and he needs to induce more groundballs. He didn’t consistently produce missed swings in the minors, which could be concerning with an increased sample size.
"In sum, we've got a flame-throwing righty with one plus secondary pitch and another average one," Sarris writes. "If we count the fastball as a plus, then we get to compare him to pitchers like Michael Fulmer and Luis Severino, two other righties with similar profiles."
The two names Sarris dropped are ace-caliber pitchers who’ve both taken another step in the last year in their mid-20s. Sarris believes the fastball flaws could limit Castillo’s ceiling, but if he’s anything close to Fulmer or Severino, the Reds would have to be quite pleased.