Catchers will come up out of their crouches, take a step forward with their right foot, then take a step forward with their left foot, then throw.
When I work with catchers, I often tell them two of the most important things they will be judged on by coaches is their ability to block pitches in the dirt, and their ability to throw runners out. Obviously there are a lot of other aspects to catching as well, but these are two of the most visible – and most glaring if a catcher isn’t good at them.
Of the two, the second one (ability to throw runners out) is the more easily measurable. At least in theory. You can throw balls in the dirt to catchers all day long in a tryout or practice situation and they can look like champs. Especially if they know ahead of time the balls are going in the dirt. But put them in a game and the question is whether they can recognize that random ball headed for the dirt fast enough to block. Tough to simulate that randomness.