Several articles I have read about the great pitcher Iron Man McGinnity say that he became a winning pitcher after he developed an “underhand” pitch, but they are not clear as to whether they mean a pitch thrown like today’s submarine pitchers or a pitch thrown like a softball is thrown. Does anyone know? And secondly, would a softball-like pitch be legal in a major league baseball game?
An effective (low-arc) softball-style delivery, is my understanding of what is meant. Like the change-up, this pitch can be disconcerting to someone expecting a different delivery. And because underhanded pitching is so relatively low-stress on the pitching arm, McGinnity was able to pitch complete games every other day, hence the “iron man” epithet.
There have been a lot of pitchers who threw a hard underhand pitch (Carl Mays and Elden Auker, to name just two) but McGinnity’s was a rising curve ball that he called “Old Sal.” It didn’t arc like a modern day slo-pitch softball pitcher might throw, but it was a relatively slow pitch. He also threw a sidearm pitch and an overhand pitch, but Old Sal was his bread and butter.
Joe McGinnity actually got the Iron Man nickname long before he reached the majors, a reflection of his off-season job in an iron foundry. He retired after an unsuccesful minor league career, but returned a few years later when he developed the underhand delivery. McGinnity eventually reached the majors at the age of 28 and stayed for ten seasons. When his big league days were over, he spent another 14 years back in the minors, finally hanging them up at age 52.
Yes, though the bigger question is whether it would be effective.
I caught in college for a guy who played professional (such as it was) fast-pitch softball in the summer. He had an undehand pitch that was quite effective when used sparingly, but because the windup and release were so slow, the second time he tried to throw it in a game it often got tagged. It had a lot of unusual movement for a baseball, but because of it’s speed (60 some mph, I’d guess) a batter could sit back on it and time it. He also threw a spitball that was much more effective.
The eephus pitch is an overhand version of the softball slow pitch. A few pitchers have used it effectively, if sparingly.
Here’s a description of his pitch, as written in a 1943 article about him. I don’t vouch entirely for it’s accuracy. I’ll look more tomorrow(gotta play pinochle tonight 
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