GOODYEAR, Ariz. — Luis Castillo’s version of the story seems too good to be true. According to the second-year Reds starter, the first time he threw his two-seam fastball was at Yankee Stadium in the second inning of his seventh big-league start. He had the bases loaded and no outs and a 3-1 count to Todd Frazier when he unfurled what would become one of the big-league’s best pitches.



Castillo, then just 24 and never having thrown a pitch at Triple-A, had impressed in his first six starts, going 1-3 with a 3.86 ERA leading into that day. He’d settled in, impressing with his 100-mph fastball, plus change and developing slider. He’d struck out 43 batters in 35 innings and walked 15.



In the eight games after the July 25 game against the Yankees, he’d go 2-3 with a 2.37 ERA with 53 strikeouts and 15 walks in 49 1/3 innings.



The difference between “promising” and “future ace” was the two-seam fastball...