Tag Up Foul Ball

Question
Bases loaded. One out.  Pop up in foul territory by third base bag in infield.  Caught by third baseman. Runner took off from his lead off and did not tag up.   Is he out if third baseman then steps on third?  I know you can tag up on foul balls hit to outfield, but what about foul balls in infield.  You cant tag up so why is he out?

Answer
Kevin,

Tagging up is tagging up, regardless of where the ball is hit to.  If the runner on third left early, then yes, the 3rd baseman can tag the base and the runner would be called out for failing to tag up properly.

Proper baseball mechanics would instruct the runner at third to stay on or very close to the bag just in case the ball is caught.

I hope this has helped.

-Martin Hoover