Can a Runner Tag Up on a Foul Ball in Fastpitch?
Yes, but only if the foul ball is caught: a caught foul fly is a legal catch, so runners can tag up and go once a fielder touches it, at their own risk. If it drops uncaught, the ball's dead, it's just a foul, and nobody can advance.
When it comes up
A batter lifts a fly into foul territory with a runner thinking about tagging up. It comes down to one thing: is it caught in the air, or does it hit the ground?
What the call is
It all turns on the catch, not on the ball going foul.
- Caught foul fly: it's an out and the ball stays live.
- Runners tag up, touch the base after the catch, then go at their own risk.
- Uncaught foul that lands: a dead-ball foul, so runners go back and nobody advances.
- Same as a fair fly: touch, wait for the catch, then decide.
- On a foul, only the catch gives you anything to run on.
Why the rule exists
A catch is a catch, fair or foul, so once the defense gloves it the play is live and the offense gets the same chance any caught ball allows. An uncaught foul is just a do-over on the count.
How it changes by age
A caught foul fly lets runners tag up and an uncaught foul doesn't, the same at every age, so younger players just need reps reading the catch.
Test yourself
Runner on third, one out. The batter pops a high foul ball near the third-base dugout and the third baseman camps under it and catches it. What can the runner do?
Show the call
Tag up and try to score.
A caught foul fly is a live-ball out, so the runner can tag her base after the catch and go home at her own risk.