A native of Portsmouth, Ohio, Nelson batted and threw left-handed, stood 5 feet 10 inches (1.78 m) tall and weighed 175 pounds (79 kg).

Prior to 1959, when he rejoined the Pirates, Nelson was a journeyman major leaguer, although he was one of the most feared hitters in minor league baseball.

Reggie Otero, manager of the Triple-A Havana Sugar Kings from 1954–1956 and later a longtime coach for the Cincinnati Reds, saw Nelson clobber major league pitchers while playing winter baseball in Cuba.

[1] It was Otero's view that, for Nelson to gain a toehold in the major leagues, he needed a manager that would show patience toward him.

[1] Before Nelson finally caught on in the majors, he had to endure two more failed tryouts with the Dodgers and the Cardinals, both in 1956, plus one more stint in Triple-A.

[1] Although his blow was not as dramatic as teammate Bill Mazeroski's home run in the same game to win the series, Nelson earned a world championship ring.

Then, in the 1952 World Series, he pinch hit in four games; in four plate appearances, he was hitless in three at bats and drew a base on balls.