This is why pitchers should NEVER allow a base runner at second base to get a walking lead on them.
When runners do this you will often hear a coach yell “Make him stop!” to the pitcher. That’s good advice because that is exactly what the pitcher needs to do.
Here is how to do it.
When the pitcher comes set and is looking back at the runner, the pitcher should just continue to stare at the runner until he stops moving. If he doesn’t or if he stops too far from the bag, just step off. DO NOT throw the pitch until the runner has stopped.
Note: This is also true for runners at third base. A runner at third who is taking a walking lead may be trying to time you for a steal of home or tipping off a suicide squeeze. Make him stop or step off.
After stepping off once or twice, the infielders should get the hint that they need to hold the runner a little more closely.