Exchange refers to the amount of time elapsed between the moment a fielder receives the ball and the moment he unleashes his throw afterward. This is most frequently applied in the following situations:
- For catchers on stolen base attempts or pick-off throws
- For outfielders on assist attempts
- For middle infielders on double-play transfers
(In the case of double-play transfers, the middle infielder's Exchange time is referred to as a separate Statcast metric known as "Pivot.")
A good Exchange can make or break a throw. Players with faster Exchange times have long been able to mask weaker arms simply because they get rid of the ball so quickly.
There's a lot that goes into a good Exchange. First, a defender must position his body and feet, so he's ready to throw as quickly as possible upon receiving the baseball. He also must field the ball and get it out of his glove and into his throwing hand in an efficient fashion.
Watch: Statcast tracks a quick Exchange time from Jason Kipnis.