There have been long-fought and dangerous disputes about the exact number of motions through which Shaw puts himself before delivering the ball.

He starts in and reverses the programme and does it over again three or four times, and just as the audience sits back in the seats with a sigh, the ball flies out like a streak.

The left-handed pitcher played Major League Baseball for six seasons with the Detroit Wolverines (1883–1884), Boston Reds (1884), Providence Grays (1885) and Washington Nationals (1886–1888).

[3] His teammates on the Charlestown team included Thomas Shea, who later became a famous ragtime composer, John Clarkson, who was later inducted into the Baseball Hall of Fame and catcher Mert Hackett.

"[9][10] Alfred Henry Spink, founder of the Sporting News, described Shaw's wind-up as follows:"After considerable swinging and scratching around with his feet, during which he would deliver a lengthy speech to the batter, to the effect that he was the best pitcher on earth and the batter a dub, he would stretch both arms at full length over his head.

"[11] After his first game for the Providence Grays, the Sporting Life wrote: "Shaw made a successful debut and promises to be a valuable man.

He has a series of introductory motions in order to get an impulse to the ball, which mystifies the batsman and conceals its pace, and will probably be a terror to left-hand hitters.

"[9] His wind-up was said to confuse batsmen and reportedly aided him in striking out the great slugger Orator Shafer five times in one game.

[13] One account suggests that it was the eccentric behavior of Dupee that created the long-running baseball stereotype that left-handed pitchers were "the 'nuts' of the game.

"[11] Shaw began his professional baseball career with the Detroit Wolverines, making his major league debut in June 1883.

[7] During a game in Boston in September 1883, Shaw's friends from Charlestown presented the rookie twirler with an elegant, inscribed gold watch, chain and charm.

[7] Midway through the season, Shaw jumped to the Boston Reds of the recently formed Union Association.

Shaw had become the Wolverines' number one pitcher and was the first National League star to jump to the Union Association.

"[16] Shaw claimed that his real reason for jumping leagues was the bad treatment he received from Detroit's player/manager Jack Chapman.

[17] Shaw also set a major league record for the most strikeouts in a game as a losing pitcher that stood for 85 years.

[20] In 1885, after the collapse of the Union Association, Shaw paid a $1,000 fine and was allowed to return to the National League as a member of the Providence Grays.

Playing a full season against National League batters, Shaw's strikeout total dropped by more than 50% to 194.

[21] In 1886, and for the second straight year, Shaw was faced with the dilemma of having played for a team, this time Providence, that folded after the season had ended.

"[28] Finally, in March 1892, Shaw, at age 32, announced that he had "most of the 'crystal' out of his arm and will be in condition soon to accept advance money.

Shaw appeared in two games for Lancaster, compiling an 0–2 record with a 4.50 ERA and nine runs (only five earned) in ten innings pitched.