He began his career as a left fielder and catcher for the Cincinnati Red Stockings, and he soon moved his way around the infield. He also played for the Columbus Solons from 1889 to 1891, and in 1892, he joined the Cleveland Spiders, where he would stay until 1898, when the owners of the St. Louis Browns were buying their players from the Spiders, who ceased to exist in 1899. O'Connor moved west to play with the Perfectos until 10 games into the 1900 season, he was traded to the Pittsburgh Pirates.
He played one season with the New York Highlanders before finishing his career back in St. Louis with the Browns. O'Connor is one of only 29 players in baseball history to date who have appeared in Major League games in four decades. He died in St. Louis at age 71.
O'Connor was the player-manager of the Browns in 1910, finishing a dismal 47–107. Cobb was leading Lajoie .385 to .376 in the batting race going into that last day. O'Connor ordered rookie third baseman Red Corriden to station himself in shallow left field.
Lajoie bunted five straight times down the third base line and made it to first easily. On his last at-bat, Lajoie reached base on a fielding error, officially giving him a hitless at-bat and lowering his average. O'Connor and coach Harry Howell tried to bribe the official scorer, a woman, to change the call to a hit, offering to buy her a new wardrobe.
At his insistence, Browns' owner Robert Hedges fired both O'Connor and Howell, and released them as players. Both men were informally banned from baseball for life. In 1981, however, research revealed that one game was counted twice for Cobb when he went 2-for-3.
As a result, his 1910 batting statistics should have been shown as 194-for-506 and .383399, less than 0.0007 behind Lajoie at 227-for-591.