Moriarty spent fifty years in baseball, making his most indelible contribution as a tough and colorful American League umpire for 22 years. As a player, he was a good fielder but only ordinary at bat. His strength was his baserunning. He accumulated 248 lifetime thefts, with a season-high of 34 for the AL 1909 champion Tigers, and stole home 11 times in his career. He joined the AL umpiring staff two years after he retired. In 1927 he took time off to manage the Tigers, succeeding his former teammate Ty Cobb. He led Detroit to fourth place in his first season but after they dropped to sixth in 1928, he returned to umpiring.
While wearing the blue, he was the object of one of Jimmy Dykes‘s most famous jibes. He called a third strike on Dykes, who then asked: “How do you spell your name?” Moriarty spelled it out. “That’s what I thought,” said Dykes. “Only one `i.’ ” When the White Sox disputed his decisions one day, Moriarty challenged them all to a fight under the stands. He decked the one player who dared step forward, breaking his hand on the player’s jaw. He retired as an umpire in 1940 and joined the AL public relations staff. His final job in baseball was as a Tigers scout. His brother Bill was a Reds shortstop for six games in 1909.