Arm Strength is defined as the maximum velocity of any throw made by a fielder. It can be used to evaluate outfielders on attempted assists, catchers on stolen base and pickoff throws, and infielders on throws across the diamond. Fielders -- especially outfielders -- often get a running start before throwing. As a result, the velocity on their throws can exceed that of pitchers, who throw to batters from the mound.
Putting a quantifiable number on the strength of a fielder's arm helps to evaluate the effectiveness of that arm. However, Arm Strength is not the only component of a good throw. Along with velocity, the accuracy of the throw is very important, as is the trajectory. A 90 mph throw from the outfield that bounces three times will inevitably lose speed each time it hits the ground.
Watch: Statcast records the Arm Strength of Bryce Harper and Michael A. Taylor on several throws from the outfield.
In A Call
"throw velocity," "He made a X mph throw"