Castillo has 15 wins, a 3.25 ERA and 218 strikeouts for a team that is below .500 and didn’t live up to its preseason goal of a postseason spot. That’s no fault of Castillo, who has been one of the breakthrough pitchers of 2019.

Why are we bringing up Castillo among the many top pitchers this season? Because he’s induced a miss on 34.1% of swings against him. That could be the highest single-season rate for any pitcher who qualified for the ERA title in the 18 seasons that we’ve been tracking the major leagues.

Going into this last start, Castillo has a precarious statistical advantage. The current mark of 33.8% was set by Kerry Wood of the Cubs in 2003. It wouldn't be surprising if Wood's mark was surpassed given the ever-increasing volume of strikeouts in the sport. Blake Snell and Patrick Corbin came close last season. Gerrit Cole of the Astros (33.6%) has nearly matched Wood with an incredible season of his own.

But regardless of that, and regardless of what Castillo does in his last start, it shouldn’t take away from the ascent he's made in 2019.

What’s made Castillo so good this season is a changeup that rates as the fourth-most valuable pitch by Fangraphs’ pitch run values. He’s thrown the most changeups of any pitcher in baseball (971 times) and induced the third-highest miss rate among the 100 pitchers who have thrown the most changeups (47%).

That pitch is the one Castillo uses to finish hitters off. He’s struck out 151 hitters with it, more than twice as many as the pitchers with the next-highest total (Stephen Strasburg and Lucas Giolito, 72). Castillo also throws a slider with a similar miss rate to his changeup (48%, which ranks ninth on that pitch's leaderboard).

His fastball induces a 19% miss rate, just above the MLB average of 18%. But he cut back on his fastball usage, barely throwing it half the time this season in favor of more changeups (he throws it nearly one-third of the time). His miss rate against the changeup jumped just over five percentage points from last season. His slider miss rate increased by seven-and-a-half.

Castillo has vaulted to 17th in the World’s No. 1 Starting Pitcher Rankingscreated by Bill James, up from 52nd prior to the start of the season. He’s part of a Reds rotation that has two other pitchers currently ranked in the top 20 -- Sonny Gray (13th) and Trevor Bauer. (19th)

We should point out that Castillo is taking on the opposite legacy of Luis Castillo, the former second baseman, whose 15-year career included time with the Marlins, Mets and Twins. Castillo, the position player, was known for his speed and for making contact at a high rate. He missed on only 5% of his swings in 2007, the fourth-lowest rate among batting-title qualifiers in the last 18 seasons.

It’s cool when everything comes (almost) full circle, isn’t it?

Captip to Alex Vigderman who suggested the ending for Stat of the Week. For more baseball content, check out the Sports Info Solutions Blog or the SIS Baseball Podcast.