First Step measures the time elapsed from bat-on-ball contact to a defender's first positive movement to the baseball. A good or bad First Step can make or break a defensive play.
There are several factors that go into most defensive plays -- such as a player's speed and efficiency. But it all starts with a good initial step.
A defender's First Step can be affected in numerous ways, including the lighting in the stadium and the angle of the ball off the bat. These factors can give a defender pause before he embarks on his route to the baseball -- and that split second could make all the difference.
In some cases a player -- like a third baseman who charges a bunt before bat-on-ball contact is made -- can have a negative value for his First Step. But such instances are rare.
First Step can also be used to assess baserunners, by measuring the time elapsed from bat-on-ball contact to the runner's first movement toward the next base.
For plays on which a baserunner attempts a stolen base, First Step measurement begins as soon as the pitcher makes his first movement.
Watch: Statcast measures Didi Gregorius' First Step on a ranging play at shortstop.
In A Call
"reaction time," "jump"