Tag up: Meaning (information, definition, explanation, facts)

In baseball, a runner must tag up if a batted ball is caught in flight. To tag up is to retouch the runner's time-of-pitch base after the ball is first touched. After a legal tag up, runners are free to attempt to advance. On long fly ball outs, runners often can gain a base; when the gained base is home base, this is called a sacrifice fly. On short fly balls, runners seldom attempt to advance.

After a caught fly ball, if a fielder can tag the runner's time-of-pitch base or the runner before he tags up, the runner is out. This often occurs on infield line drives.