Steinberg's professional career began after he was discharged from the army in 1900. He first played pro football with the Syracuse Athletic Association. While with Syracuse, Paul also played for the club's pro basketball team, making him the first Jewish basketball player. In 1902, Paul signed with Philadelphia Athletics baseball team, managed by Connie Mack. He remained with the team from 1902–1904, however he never appeared in a major league game. However, in 1902 Mack organized and coached a professional football team also called the Philadelphia Athletics. Steinberg played halfback for the Athletics, which won the Philadelphia city title, before losing the league championship to the Pittsburgh Stars. After the season, he joined the Syracuse Athletic Club in the first World Series of Football. Syracuse won the tournament held at Madison Square Garden. Steinberg joined the Franklin Athletic Club, located in Pennsylvania. The team was backed by the head of the Carnegie Steel Company was so good that they had difficulty finding opponents. That year Franklin went on to win the Pennsylvania state title. After their championship win Franklin, traveled to New York City and won the second World Series of Football. In 1905, Paul moved to Canton, Ohio and played that year with the pre-National Football League version of the Canton Bulldogs, then known as the Canton Athletic Club. In canton, Steinberg experienced the huge rivalry between Canton and the Massillon Tigers. In 1905, Massillon defeated Steinberg and Canton for the championship and Canton vowed to claim the title the following year. By 1906, Steinberg became known as the Bulldogs' best-known player and remained with Canton as one of the team's top backs. After both Canton and Massillon defeated their regular season opponents, a two-game championship was set up between the two teams. Canton won the first game, 10-5, for the team's biggest victory ever, but Massillon recovered to win the second game, 13-6, claiming the Ohio State Championship for the fourth consecutive year. After the games, however, rumors existed that some Canton players had thrown the game. Disgusted by the allegations, Steinberg quit professional football.
