Today, Major League Baseball pitchers are known for their power, striking out batters with pitches that register around one hundred miles per hour. Sure, they throw the occasional curveball, slider, and changeup to keep the hitters guessing, but the majority of top pitchers rely on their fastball.

But this hasn’t always been the case.

As the sport of baseball developed in the early twentieth century and evolved from a pastime into a major industry, pitchers devised different ways to get hitters out. Some pitchers who weren’t capable of bringing in the “high heat” came up with different ways to grip the ball, which led to the curveball and “off-speed” pitches. Among these different pitches that were developed, one of the most storied is the knuckleball.

The knuckleball is thrown by digging the tips of the index finger, second finger, and thumb into the ball. This grip gives the pitch a much slower velocity—it only travels between sixty and seventy miles per hour—and makes it wildly unpredictable and difficult to hit.

Wild is the key word.

Catchers who catch for knuckleball pitchers generally have to use a much larger mitt; knuckleball pitchers routinely give up wild pitches and passed balls, which can allow runners on base to advance and, in some cases, let the batter take first base.

Considering the obvious problems associated with throwing the knuckleball, few have mastered the pitch, but there was once a “golden era of the knuckleballers.” Jesse Haines perfected the pitch in the early 1900s and Hoyt Wilhelm followed suit in the middle of the century. Both players dominated the sport long enough to make it into the Major League Baseball Hall of Fame. But if you are reading this and know anything about the knuckleball, then you probably know about the Niekro brothers.

Phil Niekro and his younger brother Joe both had successful Major League careers from the 1960s through the 1980s: Phil amassed a lifetime 318-274 record and was inducted into the Hall of Fame, while Joe went 221-204. The brothers confused batters in both the American and National Leagues with their unpredictable knuckleballs; they even confused each other.

The Niekro brothers occasionally had to face each other in National League games as batters, and on May 29, 1976, Joe hit his only Major League homerun off his brother. Although Phil was the better pitcher statistically speaking, Joe gained more notoriety due to a humorous incident toward the end of his career.

During an August 1987 game when Joe Niekro was pitching for the Minnesota Twins at the California Angels’ stadium, the umpire noticed that the ball had some strange scuff marks on it. Well, some old-school pitchers were known to doctor balls from time to time, especially knuckleball pitchers who relied on unpredictable ball movement. When the umpire asked Niekro to empty his pockets, he did so quite demonstrably to show the umpire and the stadium that he was an innocent man. But as Niekro waved his hands in a show of innocence, the file and sandpaper he was using on the ball fell out of his pockets. The umpire caught what transpired, as did all of America, as the scene was replayed on ESPN and local sports shows for the next week. The incident earned Joe a ten-game suspension but also an appearance on Late Night with David Letterman.

After the Niekro brother retired in the late 1980s, the knuckleball was seen less and less in Major League Baseball. Boston Red Sox pitcher Tim Wakefield was one of the last notable knuckleballers before he retired in 2011, and Boston currently has another successful knuckleball pitcher on its team, Steven Wright.

If you’re a fan of the wily knuckleball, don’t worry. Wright is only thirty-four. Since knuckleballers throw with far less velocity, they can pitch well into their forties, as the Niekro brothers did.