# Spencer: Contours in batter comparisons: a trick up the sleeve

From Scott Spencer at Baseball Prospectus on August 4, 2017:

Through the eyes of writer Roger Kahn, we’ve witnessed major-league pitchers working to fool batters for ages. Regarding one Brooklyn Dodgers pitcher:

Dazzy Vance in his prime had a different trick,” [Kahn’s] father said. “For seven years he was the best strikeout pitcher in the league. Vance wore a long undershirt and he took a scissors and cut slits in the right sleeve. It ran clear down to the wrist. When Vance pitched, the long sleeve flapped. It was a white sleeve and the hitters had one heck of a time seeing that white baseball coming out of that white sleeve. Before they knew it, the fastball was in the catcher’s mitt. Strike three.” (Kahn, 1997) (1).

Kahn left to our imagination whether Vance had other tricks up his sleeve. But many things can interfere with a batter’s ability to connect (and make solid contact) with the ball: pitch speed, speed difference between pitches, break, location, peculiarities of each pitcher (whether or not observed), pitch count. And white sleeves aside, pitchers can also hide a pitch in the path of the previous pitch—called tunneling—for similar effect.

Batters need time to “read” a pitch and additional time to react to that pitch, which flies from pitcher to mitt in under half a second: the blink of an eye. If a pitcher can keep the paths of a first and second pitch together and diverge their paths only after the batter must react (about 23.8 feet from home plate, the “tunnel exit”), the batter may whiff entirely or at least miss connecting with that second pitch on the sweet spot of the bat: that’s tunneling theory. For righty-righty matchups, this article uses 2016 tunneling data on batters provided by Baseball Prospectus to explore whiff probabilities conditioned on the batter swinging, the location at the plate of the second of consecutive pitches, and the difference in those pitch paths.