Backing Up Bases
Also known as: backup responsibility, defensive backup
Backing up bases means fielders not directly in a play get behind a base or the catcher. They are there in case a throw sails past or is misplayed.
On nearly every live-ball defensive play, at least one fielder who is not fielding the ball or covering the base has a backup assignment. That fielder gets several steps behind the base or the catcher, along the throw's likely line. The goal is to keep a bad throw from rolling all the way to the fence and allowing extra bases. Backup responsibilities are usually assigned by pre-set team rules based on where the ball is hit and where runners are. They are not decided in the moment, since there is rarely time to communicate once the play is developing.
Outfielders most often back up infield throws to bases, while infielders not involved in the immediate play back up throws home. Good backup positioning requires reading the play early and getting into position quickly. A backup fielder arriving after an overthrow has already passed is functionally the same as no backup at all. The value is entirely in being in the right place before the throw, not reacting after it goes wrong.
Learn your team's backup assignments for common situations before the season starts. As a result, positioning becomes automatic rather than something you have to think through during a live play.
Example
On a throw from the outfield trying to catch a runner at third, the shortstop sprints to a position behind third base, ready to field any throw that sails past the third baseman.
Why it matters
A single overthrow that goes uncovered can turn a routine out attempt into an extra base or a run. Consistent backup positioning is a low-visibility fundamental that directly limits a defense's biggest mistakes.
Common mistakes
- Ball-watching instead of immediately moving to the assigned backup position once a play develops
- Arriving at the backup position too late, after an overthrow has already passed by
- Confusion over which player has backup responsibility because assignments were not clearly pre-established
In SwingVantage Motion Lab
Motion Lab does not track team positioning, so train backing up bases with team drills and game film.
Frequently asked questions
Who is responsible for backing up a throw to third base?
It depends on team rules and where the ball was hit. But commonly an outfielder or the shortstop, if not directly involved in the play, moves behind third base to prevent an overthrow from advancing the runner further.
Related terms
- Corner Infield PlaysCorner infield plays are how the first and third basemen defend the short game of bunts and slaps. They charge, read the hitter, and make the right throw.
- First-and-Third DefenseFirst-and-third defense is the set of plays used with runners on first and third. It tries to stop the runner on third from scoring while still getting an out.
- Middle Infield Bunt CoverageMiddle infield bunt coverage is the shortstop and second baseman's job on a bunt. They cover second and third base and back up throws as others field it.
- Pitcher's Fielding PracticePitcher's fielding practice (PFP) drills a pitcher's defensive plays: covering first base, fielding bunts and comebacker grounders, and backing up bases.
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