O'Brien spent part of two seasons with the Washington teams and Cleveland before moving to Boston. His most productive season came in 1899 as a rookie, he posted hit .282 and reached career-highs in home runs (6), RBI (51), runs (68), stolen bases (17) and games played (127). But he is best remembered as the first player to pinch-hit in a World Series game, when he struck out for Boston catcher Lou Criger in the 9th inning of Game One of the 1903 series against Pittsburgh. What O'Brien was unique in the true meaning of the word, and had the chance of remaining so forever despite his brief and undistinguished career. He was a .259 hitter in 326 games, including nine home runs with 133 RBI and 171 runs.