Obstruction Versus Interference: A Guide to Two Rules Fans Mix Up
Interference is a foul by the offense, obstruction a foul by the defense. How each is judged for runners, batters, catchers and fielders, what Type A and Type B obstruction mean, and what the penalties are.
Two of the most argued-over calls in baseball sound alike and are almost opposites. Interference is something the offense does: a batter, a runner or a coach hinders a fielder who is trying to make a play. Obstruction is something the defense does: a fielder who does not have the ball, and is not fielding it, gets in a runner's way. The penalties run in opposite directions, too. When the offense interferes, someone is usually called out. When the defense obstructs, a runner is usually given a base.
The two rules are easy to mix up because they share a section of the Official Baseball Rules (section 6.01) and because both are judgment calls. The umpire has to decide whether a contact was intentional, whether a fielder was entitled to be where he was, and what would have happened if nothing had gone wrong. This guide takes the cases in order: the batter, the runner, the people around the field, the fielder, and the catcher, who has a rule of his own. Along the way it explains the two types of obstruction and gives plain examples.
One caution before starting. This is a plain-language guide, not the rulebook. Rules differ between the professional game, college, high school and youth leagues, and the wording changes from year to year. For anything that matters, read your own league's rules and the official source at MLB.com.
The one-sentence test
Ask who did the hindering. If the player who is batting or running (or a coach for his team) hindered a fielder, it is interference. If a fielder hindered a runner, it is obstruction. That single question settles most arguments before they start.
The comparison below sets the two side by side.
| Interference | Obstruction | |
|---|---|---|
| Who commits it | Batter, runner, base coach, or an outsider such as a fan or an umpire | A fielder, including a catcher |
| What is hindered | A fielder trying to make a play | A runner's progress |
| Usual result | The offensive player is out, and the ball is dead | The runner is awarded a base or bases |
| Intent | Usually matters only for some cases | Not required; contact in the base path may be enough |
| Who decides | The umpire | The umpire |
There is one exception to the tidy division, and it deserves its own section: catcher's interference. It is a defensive foul, the catcher hindering the batter, and it is named interference even though it is committed by the fielding team. It behaves more like obstruction in its penalty, because the offense is rewarded. It is covered below.
Interference by the batter
A batter has a right to the batter's box, and he is entitled to swing. What he may not do is hinder the catcher's attempt to field the ball or to throw. The usual cases are a batter who steps out of the box and gets in the catcher's way as he throws to second base, or one who swings and then makes contact with the catcher on the follow-through in a way that stops a throw.
When the umpire rules batter interference, the ball is dead, the batter is out, and the runners return to the bases they held. There is one common exception in the rulebook: if a runner is trying to score from third on a steal or a squeeze and the batter interferes with the catcher, the runner is called out instead, with fewer than two out, and the batter stays at the plate. With two out the batter is out and the inning ends.
Notice what the rule does not say. A batter is not guilty of interference just because the catcher's throw hits him. The rulebook asks whether he hindered the play, and a batter who stays in his box and tries to stay out of the way is generally given the benefit of the doubt. The more a batter moves, the less patience the umpire has.
A batter is also out if he is hit by his own batted ball in fair territory, and the ball is simply foul if it strikes him in foul territory. These are not interference calls in the usual sense, but they are among the batter's outs that fans often confuse with them.
Interference by the runner
The runner's duties are the mirror image of the fielder's. A runner must avoid a fielder who is making a play on a batted ball, and he must not deliberately interfere with a thrown ball. The standard cases:
- Running into a fielder who is fielding a batted ball. A runner who makes contact with a fielder fielding a grounder or a fly is out, and the ball is dead. Only one fielder is protected: if two fielders go for the same ball, the umpire decides which one was entitled to field it, and the runner is not penalized for contact with the other.
- Interfering with a throw. A runner who hits or deflects a thrown ball, or who runs into a fielder about to receive a throw in a way that stops the play, can be called out.
- Being hit by a batted ball. A runner struck by a fair ball before it passes an infielder is out, the ball is dead, and the batter is awarded first base. This is not a penalty for hindering anyone; it is the rule that protects the defense from a ball that appears to have been intercepted.
- Running outside the lane. On a play at first base, the batter-runner must run in the three-foot-wide lane that begins halfway between home and first and runs along the foul line. If he runs outside it and the throw is hindered, he is out.
- Breaking up a double play. A runner who deliberately interferes with a fielder to prevent a double play can be called out along with the batter-runner. In 2016 the rules were rewritten after a hard slide in the 2015 postseason: a runner must be able to touch the base he is sliding to, may not change his path to hit a fielder, and may not slide in a way that targets the fielder.
The common thread is the word hinder. A runner who is in the base path and happens to be near a fielder has done nothing wrong; a runner who changes course to collide with one has.
Interference by coaches, umpires and fans
Offensive interference includes coaches. A base coach who touches or physically assists a runner while the ball is live can cause the runner to be called out. This is why third-base coaches wave their arms rather than grab a runner at the base.
An umpire can interfere too. If a batted ball touches an umpire in fair territory before passing a fielder, the ball is dead. If an umpire hinders a catcher's throw while a runner is stealing, the ball is dead and the runner goes back, unless the throw would have retired him anyway. Neither case is a penalty on anyone; the rules simply restore the situation.
Spectator interference is a different matter. Fans in the stands are not part of the game, and a fielder is allowed to reach into the stands for a ball. But if a fan reaches over the wall into the field of play and touches a ball that a fielder might have caught, the umpire can call interference and declare the batter out or put runners where he thinks they would have been. Two famous cases turned on this. In the 2003 National League Championship Series, a fan reached for a foul ball near the stands in Chicago, and the umpire ruled that the ball was over the stands and the call was not interference. In the 1996 American League Championship Series, a young fan reached over the fence in right field in New York and deflected a fly ball that was ruled a home run. In both cases the call turned on the umpire's view of where the ball was and whether a fielder could have caught it.
What obstruction is
Obstruction is defined narrowly. It is the act of a fielder who, while not in possession of the ball and not in the act of fielding it, impedes the progress of a runner. Each of those conditions matters.
A fielder with the ball can stand in the base path and tag the runner. The runner has to go around him or be out. A fielder in the act of fielding a batted ball has the right of way; a shortstop going to his left for a grounder can collide with a runner without penalty, and the runner is the one who has to avoid him. A fielder who is about to receive a thrown ball, with the ball in flight and close enough to be a threat, can also be treated as in the act of fielding it.
What the fielder may not do is stand on the base line without the ball and without a play in progress. A fielder who has already missed a batted ball is no longer in the act of fielding it, and he must clear the path. A first baseman who steps onto the runner's path before the throw comes, or a third baseman who drops to a knee in front of a runner heading home, has committed obstruction if the runner is slowed down or forced to alter his path.
There is no requirement that the fielder meant to do it. The rule protects the runner's right to run the bases. Contact is the usual evidence, but the umpire can also rule obstruction if a fielder's position forced a runner to veer or stop without contact.
Type A and Type B obstruction
The rulebook splits obstruction into two types, and the split is the heart of the rule.
| Type A | Type B | |
|---|---|---|
| Situation | A play is being made on the obstructed runner | No play is being made on the obstructed runner |
| Ball | Dead immediately | Delayed dead ball; play continues |
| What the umpire does | Stops play, awards bases | Lets play finish, then awards bases if needed |
| Minimum award | At least one base beyond the last base the runner had legally touched | Whatever bases it takes to undo the harm |
Type A happens when a fielder with the ball is trying to put out the obstructed runner, or a throw is on the way to do so. A third baseman gets in front of a runner heading home as the catcher gets the ball, and the runner is caught between. The umpire signals and calls time, the ball is dead, and the runner is awarded at least one base beyond the last base he touched before the obstruction, along with any other runner the umpire thinks would have advanced further.
Type B happens when the obstruction occurs and the defense is making a play elsewhere. The umpire points at the fielder, but play continues. When it ends, the umpire decides whether the obstructed runner reached the base he would have reached without the obstruction. If so, the call changes nothing. If not, he is awarded that base.
The Type A rule produced one of the most unusual game endings in World Series history. In the third game of the 2013 World Series, St. Louis's Allen Craig, trying to score, was tripped by Boston third baseman Will Middlebrooks, who had dived for a throw, the umpire called obstruction, and the Cardinals won 5-4. The play was Type A in nature: a play was being made on the runner, and the runner was awarded the base he would have reached.
Catcher's interference
Catcher's interference is the exception to the rule that defense obstructs and offense interferes. It occurs when the catcher or another fielder hinders the batter's ability to swing, usually by touching the bat or reaching in front of the plate. The classic case is a catcher who sets up too close to the batter and brushes the bat on the follow-through.
The penalty favors the offense. The batter is awarded first base, and any runner forced to advance by his taking first moves up. The batter is not charged with an at-bat, and the catcher is charged with an error. The plate umpire signals and play continues so that the offense can choose the outcome if it prefers: if the batter hits the ball and reaches base safely and every runner moves up at least one base, the manager can decline the penalty and let the play stand. This option exists because a batter who hits a double despite the interference should not be forced to settle for first base.
If a runner is trying to score from third on a squeeze play or a steal when the catcher interferes, the ball is dead, the pitcher is charged with a balk, the runner scores, and the batter is awarded first. That rule is why a catcher is careful not to crowd the plate on a suicide squeeze.
Catcher's interference is separate from the rule on plate collisions. A rule adopted in 2014 forbids a catcher from blocking the plate without the ball and a runner from deviating from his path to knock the catcher over. A catcher who has the ball, or who is in the act of fielding a throw, may stand in the path; a catcher who blocks the plate without either may be called for obstruction, and the runner is ruled safe. The rule was written with player safety in mind, and it has changed the way plays at the plate are made. A related piece on how umpires decide which kind of play they are watching is force plays and tag plays.
Worked examples
Here are six situations, with the ruling a plate or base umpire would typically make.
- A runner on first takes a wide route to second and runs into the shortstop fielding a ground ball. Interference. The runner is out, the ball is dead and the batter is awarded first base.
- A runner heading for third is slowed by the third baseman standing in the base line without the ball while the throw is going to second. Type B obstruction. Play continues; when it is over, the umpire sends the runner to the base he would have reached.
- A runner rounding third is tripped by a third baseman who has lost track of the throw, and the catcher then tags him. Type A obstruction. The ball is dead and the runner is awarded home.
- The catcher's mitt hits the bat on a swing. Catcher's interference. The batter is awarded first base.
- A batter steps out of the box and his bat knocks the catcher's throw to second off course. Batter interference. He is out and the runner returns.
- A fan reaches over the wall and touches a fly ball in play. Spectator interference. The umpire may rule the batter out or place runners.
What an umpire does and what replay does
An umpire who sees interference calls time and states the ruling. An umpire who sees obstruction points at the fielder and says "that's obstruction"; for Type A he calls time at once, and for Type B he waits for the play to end. Players and managers can ask questions, but the call is a judgment and the umpire explains it at his discretion.
Some of these calls can be reviewed in the professional game, and others cannot; which is which has changed over the years, and the details are in the guide to instant replay and the challenge system. If you are watching and wonder why a play was or was not reviewed, check the current league rules rather than assume.
The same attention to judgment applies to a related question, whether a runner is allowed to leave a base after a catch, which is set out in tagging up and the sacrifice fly. Many rules in this part of the book depend on the same question: where was the ball, and who had the right of way?
Rules in youth and amateur baseball
The Official Baseball Rules govern the professional game, and amateur codes differ. Youth leagues, high school federations and the NCAA each publish their own books, and some add special rules for contact between runner and fielder. Little League and others, for example, have rules about unsportsmanlike or malicious contact that go beyond the professional definition. A coach who needs to teach the topic should look at the book that governs his league and at the governing body's own materials, such as Little League International. The site's youth section, at youth baseball, collects further material.
Common questions
Is obstruction always a penalty on the fielder? Yes, in the sense that it is a foul by the defense, but the penalty is a base award to the runner, and sometimes no award is needed if the runner reached the base anyway.
Can both fouls happen on one play? They can. A runner might run into a fielder who was already standing in his path without the ball. The umpire has to decide which came first, and if the obstruction came first, the runner is protected.
Does the runner have to be touched for obstruction? No. Impeding his progress is enough, though contact is the clearest evidence.
Why is catcher's interference called interference? Because it is the catcher hindering the batter's swing. It is listed with interference, though it is the defense that commits it.
Who decides whether a fielder was fielding the ball? The umpire, on the field, in real time. That is why the same play can look different from the stands and from the base path.
Can fans be penalized for interference? The umpire's ruling is applied to the play: the batter may be called out or runners placed where the umpire thinks they would have been. Whether a fan is removed from the park is a decision for the club and its security staff.
Where to go next
If you came here after an argument about a specific play, the easiest next step is to read force plays and tag plays and the guide to instant replay, which cover the calls that sit next to these two. The topic page on rules and umpiring collects further coverage, and the strike zone article covers the other judgment call that fans never stop arguing about.