What is a Balk in Baseball? And, the statistics Behind Balking

At TheDataJocks, we like to focus on statistics but more broadly we’re all about gaining a deeper understanding of the games we love. Today we’re going to look at one of the most commonly asked questions: What is a balk in baseball?

The most surprising thing I learned in researching this article is that there are thirteen different actions that constitute a balk. And, one of these 13 different actions is simple “the pitcher commits an illegal pitch”. This is one of the reasons defining a balk in baseball is so difficult; a single clear, concise definition does not exist.

We’re going to start by looking at the definition of a balk and the 13 ways you can commit one. But we’re also going to give this one the TDJ treatment by looking at how the advanced statistics (including RE24!) interact with balking. Finally, we’ll talk about the relationship between balking and stolen bases.

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What is a Balk in Baseball?

Nothing makes my heart race more than when somebody asks me to explain balking. I can’t do it. This isn’t unique to me; one of my favorite memes from bleachernation is centered around the idea that the rules of balking are extraordinarily vague:

I find the following video from the Baseball Tonight crew to be pretty good at conveying the salient points of balking. Here they are trying to answer what balking is.

But even this video could use a lot more details, let’s look at what the rule book actually says.

13 Ways to Balk in Baseball

The MLB website describes a balk by the phrase “a balk is when a pitcher makes an illegal motion on the mound that the umpire determines to be deceitful”. The rules describing what is a balk in baseball are found in Section 6 of the official MLB rules. Section 6.02(a) actually describes THIRTEEN distinct ways for a pitcher to commit a balk.

This is one of the reasons that answering “What is a balk in baseball” is so difficult. There is no one definition of a balk. Balks generally cover 13 different actions which all fall under “illegal motion that the umpire determines to be deceitful”. We’re going to separate these 13 ways to balk in baseball into a few groups to help understand them more easily.

Illegal “Fake” Throws

Rules 6.02(a)(1), (2), and (4) deal with not actually throwing the ball when it looks like you’re going to throw it. Here are the exact wordings:

• The pitcher, while touching his plate, makes any motion naturally associated with his pitch and fails to make such delivery
• The pitcher, while touching his plate, feints a throw to first or third base and fails to complete the throw
• The pitcher, while touching his plate, throws, or feints a throw to an unoccupied base, except for the purpose of making a play

The key in all three of these rules is that for the balk to occur, the pitcher must be touching the rubber. If he is, then pretty much any fake throw results in a balk. However, closely reading these rules, it seems as if a fake throw to second base from the rubber is allowed if there is a runner on this base.

See why the balk rules are so confusing?

Illegal “Real” Throws

In addition to faking throws to bases, you also cannot make a seemingly real pitch without satisfying a few criteria. This is the content of rules 6.02(a)(5)-(7),(9).

• The pitcher delivers the ball to the batter while he is not facing the batter;
• The pitcher makes any motion naturally associated with his pitch while he is not touching the pitcher’s plate;
• The pitcher, without having the ball, stands on or astride the pitcher’s plate or while off the plate, he feints a pitch;
• The pitcher makes an illegal pitch;
  • Notice, this rule is so vague that basically anything could be a balk. The example given is a “quick pitch”. I believe the point of this rule is to give the umpire leeway to call balks in unprecedented scenarios.

Each of these rules together cover the fact that the pitcher is not allowed to deceive the batter as to whether or not he is about to throw the pitch. This is interesting because most people associate balks with illegal pick-off moves but there are other types of balks as well.

The next group of balk definitions deals with how the pitcher handles the ball when on the rubber.

Illegal Ball Handling

Rules 6.02(a)(10)-(11) further restrict what the pitcher is allowed to do in his normal course of a pitch. If the previous set of rules dealt with fake pitches, these rules deal with what happens with the ball itself even if a pitch isn’t faked. The rules read as follows:

• The pitcher, after coming to a legal pitching position, removes one hand from the ball other than in an actual pitch, or in throwing to a base;
• The pitcher, while touching his plate, accidentally or intentionally has the ball slip or fall out of his hand or glove;

Again, the point of these rules is to limit the ability of the pitcher to perform any pick-off moves in a deceitful way. The rules describing what is a balk in baseball aren’t limited to “you can’t do this or that”. The next set of rules specify something that you have to do in a pick-off move.

Proper Pitching and Pick-Off Motions

These two rules tell us how a pitcher must control his body when in the normal course of pitching. Rules 6.02(a)(3) and (13)

• The pitcher, while touching his plate, fails to step directly toward a base before throwing to that base;
• The pitcher delivers the pitch from Set Position without coming to a stop

The first rule says that a pick off move must be done while stepping directly towards the base! This is likely the most common cause of a balk and is perhaps the best thing to remember when thinking about the rule surrounding what is a balk in baseball.

Similarly, rule (13) says that the pitcher must come to a complete stop before delivering the pitch. Personally, I would have combined this rule with rule (5) “the pitcher makes an illegal pitch”, but OK.

The Oddities

There are two final rules of balking that don’t neatly fall into any of the other categories. These are rules 6.02(a)(8) and (12). They read:

• The pitcher unnecessarily delays the game;
• The pitcher, while giving an intentional base on balls, pitches when the catcher is not in the catcher’s box;

The first of these rules I totally understand. There should be some penalty for delay of game. If we want to call it a balk, so be it.

But rule (12)…What? How about a more general rule where a pitch requires the catcher to be in the catcher’s box period. In any case, if the pitcher and catcher decide to have a game of catch off to the side half way through an intentional walk sequence, then a balk shall be called!

Now that we understand what a balk is in baseball (or, at least, now that we’re closer to understanding), let’s look at some statistics and data surrounding balks.

Balks and RE24

One of the best tools in baseball is RE24 and the run expectancy matrix. The run expectancy matrix tells us how many runs are “expected” to be scored for the rest of the inning given how many outs there are and what runners are on which bases. For example, with a runner on 2nd and no outs, the average runs scored per inning is 1.068. With no outs and nobody on, the expected runs are 0.461.

The run expectancy matrix helps us put a “run value” on specific actions. By looking at the expected runs before and after an at-bat, you can determine how much a player’s actions helped or hurt their team. In the last section, the difference between “no outs, nobody on” and “no outs, runner on 2nd” is 1.068-0.461=0.607 runs. Therefore, a lead off double to start an inning has added about 0.6 runs to your team’s expected score.

We can use this tool to determine how bad a balk is! A balk advances all runners on by one base. Therefore, we can value a balk by comparing the run expectancy before and after all runners advance a base. Let’s show an example of how this works.

If there is a runner on 1st with nobody out, the run expectancy is 0.83. With a balk, the runner advances to 2nd with nobody out – a run expectancy of 1.068. This means that the value of the balk is about -0.23 runs for your team. That is, you hurt your team to the tune of about a quarter run on average.

On the other hand, balks often occur because pitchers are trying to be as quick as possible with their pick-off move. If the runner is successfully thrown out at first, the run expectancy drops from 0.83 to 0.243. That means a pick-off in this setting adds about 0.59 runs of value to the fielding team on average.

These numbers allow somebody to determine the risk/reward profile for extremely aggressive pick off moves. For example, if your aggressive pick off move adds 5% chance to pick-off the runner but also a 5% chance of a balk, this is actually a net positive! This is because picking the runner off adds more value than the balk takes away.

This is yet another example of how to use the run expectancy matrix to make decisions in baseball as I’ve shown in this article here.

Balking and Picking Off Runners

Finally, I wanted to look at some statistics surrounding balking. In particular, I wanted to investigate the correlation between balking in baseball and pick offs. The point of the balking rule is to prevent pitcher’s using deceptive movements or motions to catch baserunners off guard. It is in the interest of fairness.

Balks and pick-offs are correlated. The player with the most all-time balks is Steven Carlton with 90 career balks, 79 of which came when playing for Philadelphia. It turns out, though, that Steve Carlton leads the all-time pick-off list too with 145 over the course of his career. By and large I think this trend will hold true: pitcher’s who commit more balks do so because they have more aggressive pick-off moves. More aggressive pick-off moves also tend to catch more runners.

The data is confusing though, I recommend checking out the statistics given here which correlate the number of balks with the number of stolen bases. I’ll provide a quick summary below.

In both 1950 and 1988, the MLB changed the rules surrounding balking to make it more advantageous for the runners. In the 1988 season, even the players had trouble deciphering our original question “what is a balk in baseball” and that season set a record for the most balks. You can see long-term trends between stricter balk rules and more stolen bases from the 1950s up through the late 80s.

However, if you correlate balks with the number of stolen bases over longer periods of time, the results are mixed. If you would expect more balks = fewer stolen bases, this largely isn’t the case. In fact, the two data streams seem largely uncorrelated with each other. However, one could argue that this is because the stolen base statistics are skewed by differing strategies over time. Balks aren’t the only thing that correlate with stolen bases.

That is all to say, even the data is mixed about how to interpret balking in baseball. What is a balk? What effects do the rules around balking have? We can guess and look closely at the rules and statistics, but truly balks remain one of the most confounding things in sports.

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