Infield Fly Rule and Balk Explained: Baseball's Two Most Confusing Rules

Baseball's rulebook is full of oddities, but two rules confuse fans more than any others: the infield fly rule, which makes a batter out on a ball nobody caught, and the balk, which gives runners a free base when the pitcher flinches. Here is how both work.

The Infield Fly Rule

The infield fly rule says the batter is automatically out on certain pop-ups, even if the ball is dropped. It applies when all of these are true:

1. There are fewer than two outs.
2. Runners are on first and second, or the bases are loaded.
3. The batter hits a fair fly ball (not a line drive or a bunt).
4. An infielder can catch it with ordinary effort.

The umpire signals by pointing up and calling "Infield fly, batter's out." If the ball is near a foul line, the call is "Infield fly, if fair."

Why the Rule Exists

Without it, an infielder could let an easy pop-up drop on purpose. The runners, who had to stay near their bases in case of a catch, would then be forced to run, and the defense could turn an easy double or triple play. The rule protects the offense from that trick.

What Runners Can Do

The ball is still live. Runners can advance at their own risk, exactly as on any caught fly ball: if the ball is caught, they must tag up first.

The Balk

A balk is an illegal motion by the pitcher with runners on base. The rules exist to stop pitchers from deceiving baserunners about whether they are throwing home or trying a pickoff.

Common Balks

• Starting the pitching motion and stopping without throwing
• Not coming to a complete stop in the set position before pitching
• Faking a throw to first base while touching the rubber
• Throwing to a base without stepping toward it first
• Dropping the ball while on the rubber
• Pitching while not facing the batter

What Happens After a Balk

Every runner is awarded one base, and a runner on third scores. If the pitcher still delivers the pitch and the batter reaches base safely, with every runner also advancing at least one base, the play stands and the balk is ignored. Otherwise the balk is enforced.

Balks and the Pitch Clock

The pitch clock era limits how often a pitcher can step off or throw over to a base in a single plate appearance. Going past the limit without getting the runner out counts as a balk. Learn more in our MLB pitch clock rules explained.

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