When defending, you can get out by throwing a pick-off ball when the opponent tries to steal.
You can throw a pick-off ball by tapping the right base before pitching. It cannot be thrown on a base without a runner.
You can check Speed of your opponent by looking at the numbers on the base.
Stolen Base Caution Player-card
Basically, all Player-cards with high Speed ability score should be careful.
These two Player-cards need to be especially careful because the skill is activated by stealing the base.