With the final pitch of this past world series in the book, we now have two iconic series-ending takes in recent memory. Miguel Cabrera was frozen by a Sergio Romo fastball when he was perhaps thinking slider, and Carlos Beltran famously flinched at an Adam Wainwright curveball in game seven of the 2006 NLCS.
Of course that’s just two data points, connected only tenuously by situation (last out) and outcome (strike three taken), but it is enough to spawn a digression. Even if it would be kind of crazy to find out that batters swing less often as your average game progresses based on this starting point, crazier things have been born of less consequential moments.
With the help of sabermagician Jeff Zimmerman, I set out to answer this question. Seems easy enough. How often to batters swing, by inning? Let’s limit it to at-bats against starters, considering the difference between a starter making his way through the lineup again in the sixth inning and a fresh reliever in the same inning.
Um. So we’re done here? This was run late in the season, but the “n” in even the smallest bucket is well over 5000. And there go the swing percentages, declining steadily as the game goes on. Easy enough to see.
Except that it’s entirely possible that the pitchers are throwing fewer strikes as the game goes on. Let’s check how often the starters chuck it inside the zone, by inning:
Okay so batters are swinging less against starters as the game goes on, but it might only be because they’re seeing fewer strikes. What happens if we add the relievers back in?
batter swing %
reliever zone %
Ah-HAH. The declining swing percentage thing goes right out the window. When it comes to late innings against relievers, batters and pitchers both reset their their swing and zone percentages respectively.
If there is an interesting string to follow here in the future, it is the slight chance that starters who remain in the game past the fifth inning begin playing some sort of cat-and-mouse game, where they throw the ball in the zone less and the batters leave the bat on their shoulders more. Could there be a general relationship between batters faced, and zone and swing percentages? We’ll keep looking.