Phil Niekro — American Athlete born on April 01, 1939,

Philip Henry "Phil" Niekro, nicknamed "Knucksie", is a former Major League Baseball pitcher. He was inducted into the Baseball Hall of Fame in 1997. Niekro's 318 career victories are the most by a knuckleball pitcher and he ranks 16th on the overall all-time wins list. He also won the National League Gold Glove Award five times. Niekro pitched for 20 seasons for the Milwaukee and Atlanta Braves. During his tenure in Atlanta, Niekro was selected for five All-Star teams, led the league in victories twice and earned run average once. Niekro was also a key to the only two division titles Atlanta won before 1991... (wikipedia)

I never knew how to throw a fastball, never learned how to throw a curveball, a slider, split-finger, whatever they're throwing nowadays. I was a one-pitch pitcher.
I would think every organization has pitchers who have good talent but just don't have what it takes to make it with what they've got.
My dad played for a coal-mining team in eastern Ohio; he was a very good pitcher. If he hadn't hurt his arm, he probably would have got a shot somewhere. He hurt his arm one spring, didn't warm up good enough, couldn't throw a fastball anymore. Another coal miner taught him how to throw the knuckleball.
There aren't many hitters who like facing knuckleball pitchers. They may not be intimidated by them, but they sure are thinking about them before they go into the box.
I remember going to see my dad pitch against other coal-mining teams, and he was successful with the knuckleball. I saw how bad guys would look like swinging, and how guys talked about how he could throw every day and didn't hurt his arm. That's how I grew up learning.