This is an incredibly simple but extremely valuable drill.
Catchers have a lot of roles to play on the field. They help the pitcher, command the defense, and also serve as the stalwart defenders of home plate. The catcher is effectively the first line of defense on every play, and the last line of defense whenever the opponent threatens to score.
Blocking wild pitches is therefore an extremely valuable skill for every catcher to have. Effectively preventing passed balls can stop runners from advancing and scoring while also giving the pitcher more confidence in breaking balls and borderline pitches.
Even the best pitchers get a little wild sometimes. Other times, the situation just calls for a curveball in the dirt or a hard slider low and away. Whether intentionally wild or not, pitchers need to know they've got a wall behind that plate. Catchers need to be drilled in the proper way to block a ball.
There's no better way to teach a catcher than to just put him in the crouch and start chucking balls in the dirt.
Catching gear, bucket of baseballs.
Executing the Drill
Put your catcher behind the plate in full gear - don't forget the mask. Stand about 30 feet away with a bucket of baseballs.
One ball at a time, deliberately throw pitches in the dirt so the catcher must drop and block.
Reinforce the fundamentals - drop to the knees, get behind the ball, corral the ball and try to deaden it, keep the head down and locate the ball as soon as possible. Some young catchers will be afraid of the ball and might turn their faces away just as the ball comes in. Make sure you help your players overcome that fear, the mask is there for a reason and your catchers will do a better job if they keep their eyes open and focused on the ball.
Encourage excellence. The goal here is not to simply stop the ball from getting by the catcher. The best catchers bring wild pitches under control. They knock the ball straight down in front and they are quick to pick the ball up. When runners on base can see the ball has stopped in front of the catcher, they are less likely to risk taking an extra base.
Make it Fun
An easy way to make this drill more fun, turn it into a game. We call it the "Goalie Game" and its pretty self-explanatory. If you have more than one catcher, pit your catchers against each other.
Create a "goal" area for each catcher to guard. Now, have the catchers take turns throwing balls in the dirt at each other. Every time a catcher fails to block a ball thrown within the goal area, the other catcher scores a point. As your catchers develop their skills, expand the goal area to make this drill more challenging.
When pitchers begin throwing breaking balls and other off-speed pitches, catchers need to practice how to block those pitches as well. All you need to do is incorporate those pitches into this same drill. Throw the ball with some spin on it, try different grips, and change speeds.
This will help your catcher develop a sense for how the ball reacts when it hits the dirt with some extra movement on it. The bounce of a fastball is pretty straightforward, but breaking balls can react much more erratically.