Luck

Luck is often mentioned but seldom defined when baseball is discussed. "Luck" is usually applied to events that either do not rely on skill, or that defy normal probabilities, and can be an explanation for a particular outcome when all other explanations fail (it then gets qualified as "dumb" luck or "plain" luck).

Luck, as opposed to skill, can refer to an outcome that is so rare that it is not the result of hard work or practice. For example, a number of double plays (or even triple plays) result from a hard-hit line drive hit directly at a defensive player standing near an occupied base. While there is some skill involved in catching the ball cleanly, in many cases, if the ball had been hit only a few inches in a different direction, the outcome of the play would have been completely different. The same can be said of a pitcher who ties up a hitter with a pitch, but the poorly-hit ball still manages to fall for a hit. In this case, "hit probability", as measured by Statcast, can quantify how lucky an outcome that is.

Luck can also refer to a rare random event that just happens to occur in a critical situation. Examples would be home runs hit at critical times by players who hardly ever hit any: pitcher Mickey Lolich hit his only career homer in one of just three career World Series starts; he made 496 regular season starts without ever going deep. No predictive model could have come up with this outcome.

Another example of luck is defying normal probabilities. It has been demonstrated that batting average on balls in play tends to be relatively stable, both for hitters and pitchers, but there are always outliers whose statistics for a time are particularly good or bad. This can be said to be simply luck, as such performance is not repeatable and everyone will naturally tend to gravitate back towards the mean.

The Pythagorean Theorem of Baseball is another area where luck can be observed. The formula will almost always accurately predict a team's won-lost record based on the number of runs they score and allow. However, a few teams deviate from this for short periods. This is generally due to luck, although sometimes some actual skill factors such as the presence or absence of a strong bullpen can have a moderate effect. But in almost all cases, teams will revert to the means as luck, when it is present, is impossible to reproduce or maintain.

Further Reading

• Jim Albert and Jay Bennett: Curve Ball: Baseball, Statistics, and the Role of Chance in the Game, Copernicus Books, New York, NY, 2001. ISBN 978-0387988160
• Irwin Nahinsky: "Luck, Skill, and Head-to-Head Competition in Major League Baseball", in Baseball Research Journal, SABR, Vol. 49, Nr. 2 (Fall 2020), pp. 58-65.