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Baserunning does not always get as much attention as some of the other aspects of baseball, like hitting, pitching, and fielding. However, good baserunning is a critical skill for any baseball player to have. A runner must always have their head in the game and be prepared to make their next move at a moment’s notice. Oftentimes, that means being prepared to tag up on a ball that is caught in the air.
In baseball, tagging up is when a runner returns to touch the last base they occupied before they can advance to the next base. A runner must tag up any time a fielder catches a ball in the air before it bounces on the ground. This includes balls caught in the infield, the outfield, and in foul territory.
Tagging up may seem like an oddly specific rule, but it is actually a very important part of baseball and something that you’ll see in almost every game. It is pretty common for base runners to advance on a fly ball after tagging up, especially when they are at third base. When a baserunner tags up from third and scores on a fly ball to the outfield, the batter is credited with hitting a sacrifice fly.
Why Do Baseball Players Have to Tag Up?
Baseball players have to tag up so that they are not thrown out at the base they previously occupied. If a runner proceeds to the next base without tagging up, the opposing team can throw the ball back to the runner’s original base, and if the ball reaches the base before the runner, the runner will be called out.
If a runner does tag up, however, they will then have the opportunity to advance to the next base. This often means scoring a run from third base on a sacrifice fly.
What Happens If a Runner Does Not Tag Up?
If a runner proceeds to the next base without properly tagging up, he may be out. However, it is up to the other team to record the out. The umpires will not call the runner out simply because he failed to tag up.
Therefore, it is possible for a runner to advance safely without tagging up, and it is even possible for a runner to score without tagging up. If the opposing team does not throw to the runner’s original base and have one of their fielders stand on the base with the ball in his glove, the runner will not be called out. Once the pitcher has thrown his next pitch, it becomes too late for the defensive team to retire the runner.
When Can a Runner Leave the Base?

A runner can leave the base as soon as the ball is touched by a player on the defensive team. The fielder does not need to have legally caught the ball as long as they have made contact with it. In other words, the defensive player does not need to have secure possession of the baseball — this is a common misconception.
If fielders needed to have properly caught the ball before runners could tag, then defensive players might purposefully bobble the ball just to prevent runners from advancing. To prevent this, baserunners are allowed to take off as soon as the ball makes contact with a fielder’s body or glove.
A runner can also leave the base before the ball is caught, but they must return to touch the base after the fielder has secure possession of the baseball. As long as they have done this, a runner is free to proceed to the next base for as long as the ball is in play.
What Happens If A Runner Leaves the Base Too Early?
If a runner leaves the base too early, the opposing team can make an appeal to the umpire. This process involves throwing the ball back to the base the runner originally occupied and seeing if the umpire calls the runner out.
If the umpire calls the runner safe but the defensive team still believes the runner to be out, they may use replay review to challenge the call on the field. If the replay shows the runner did indeed leave the base early, the call on the field will be overturned and the runner will be called out.
It is important to note that a tag-up is a time play and not a force play. This means that any runs scored before a runner is caught for leaving too early will still count, even if the runner is eventually caught and called out. For example, if a runner leaves second base too early and is caught before they tag up, but by the time they are caught the runner from third has already scored, the run scored on the play is counted.
Why Does the Tag Up Rule Exist?
The tag-up rule might seem confusing and overly complicated, but it actually exists for a simple and practical reason: it prevents runners from advancing too far on balls hit in the air.
Without the tag-up rule, runners could move up several bases on a high fly ball. Indeed, even a lazy pop-up to the outfield has the potential to clear the bases if it hangs in the air long enough. Thus, if runners didn’t have to tag up, batters would be incentivized to hit high fly balls with runners on base instead of trying to get a hit. To prevent this from happening, the tag-up rule was instituted.
Related Questions
Why Don’t Runners Tag Up With Two Outs?
Usually, on a fly ball, runners will wait close to their original base so they can return in case they need to tag up. However, you might notice that this does not happen when there are two outs. Why might that be?
When there are already two outs, runners do not have to worry about tagging up. If a fielder catches the ball, the inning will be over. If no one makes the catch, then there is no need to tag up. Therefore, the smartest thing for the runners to do is to run as fast and as far as they can on a fly ball with two outs.
Why Do Fielders Sometimes Drop a Fly Ball on Purpose?
Occasionally, you might see an infielder drop a fly ball on purpose. This seems confusing, since catching a fly ball is an easy way to record on out. Sometimes, however, because of the tag-up rule, it is actually in the infielder’s best interest to let the ball hit the ground.
Because of the tag-up rule, runners cannot advance all the way to the next base on a fly ball. They have to wait by their original base in case they need to tag up. This means that if the infielder does drop the ball, the runner has to scramble to the next base as fast as possible. Therefore, if the infielder drops a fly ball, they can sometimes turn a double play by picking up the ball, and catching both runners with force plays instead. Usually, this type of trick double play only works if the batter isn’t running to first base fast enough.