Baseball, in its modern form, was developed in the mid 1800s, played initially under rules written by Alexander Cartwright who is heralded by many as the father of modern baseball. Cartwright’s guidelines, called the “Knickerbocker Rules,” standardized what had previously been a series of variations of the same game. These new rules catapulted the game into mainstream culture and, by the 1850s, the game was being called the “national pastime.” But that game looked very different from the baseball of today.

One of the most notable differences between the game played under Cartwright’s rules and today’s game is the role of the pitcher. The position got its name because the job of the player was to toss the ball underhand, or “pitch” the ball toward the batter. The pitcher’s role was minimal; competition was between the batter and the fielders, which, as you can imagine, made for a very exciting game.

Then, in 1884 (the same year that the last African-American player was allowed to play in American professional baseball until Jackie Robinson played for the Brooklyn Dodgers in 1947), a major rule change occurred. As a result, pitchers were allowed to throw pitches overhand. With this, a new component was added to the competition: the battle between the pitcher and the batter.

Now here we are, more than a century later, and that one alteration has changed everything about our game. Pitching is now the most analyzed aspect of baseball, while fielding remains the most overlooked. And not only did the change transform the way the game is examined, it also changed the way the game is played.

Before the rule change, the only result of an at-bat in which no fielders were involved was a home run. But with the introduction of the battle between hitters and pitchers, two more possible outcomes were created: strikeouts and walks. These three results of an at-bat that do not involve any fielders are called the Three True Outcomes (TTO).

The Three True Outcomes began being recorded in 1910, and the frequency of one of the TTOs occurring was about 13 percent. Then, the frequency at which the TTOs occur has increased at a rate of about one percent every seven years. This rate of increase has accelerated in the modern era, with the frequency of TTOs increasing about one percent every five years since 1980.

In 2012, the frequency of TTOs surpassed 30 percent for the first time. The 2012 season featured pitchers such as Aroldis Chapman and Craig Kimbrel, whose frequency of TTOs were 48.5 percent and an incredible 56.3 per cent, respectively.

So far in 2013, the trend has continued, with the frequency of the TTOs at an all-time high of 31 percent. With the rise in the use of baseball analysis in front offices and clubhouses, this trend will continue at a faster pace. Experts are now appreciating the value of walks, which has been underestimated, as well as recognizing that the detriment of striking out has been exaggerated. With these realizations, we won’t see a slowdown in the increase of TTOs.

Why does this matter? Because a high incidence of plays that do not involve the fielders results in unexciting baseball. If the trend continues so that every pitcher is at the level of Chapman and Kimbrel, then major league baseball might be looking at a serious viewer and attendance shortage. That type of baseball simply wouldn’t be exciting for nine innings every day. Serious rule changes would need to be considered to shift the focus of the game away from the pitcher and hitter and back to a contest between the hitter and fielders, the way Cartwright originally envisioned the game.