Nine players who had come from UNC had played in Major League Baseball before Mule Shirley came along in 1924. Pitcher Bob Lawson was the first, playing in his first game all the way back in 1901. The most successful up to that point was probably Larry Woodall, who was in the midst of a 10-year career when Shirley made the majors. Moonlight Graham is the most famous Heel of that era, albeit for reasons deeper than just his play on the field.
However, Mule Shirley can claim something none of those three can.