Tommy O'Brien was a professional baseball player known for his time as a pitcher in the early 20th century. He played in Major League Baseball (MLB) primarily for the Chicago White Sox and the New York Giants. O'Brien made his MLB debut in 1910 and had a career that spanned several seasons, showcasing his skills on the mound. Throughout his career, O'Brien was recognized for his competitive spirit and contributions to his teams. He played during a time when baseball was evolving, and his performances helped shape the game. O'Brien's legacy remains a part of baseball history, particularly for fans of the teams he represented.