McDermott dropped out of high school after just one year, and was picked up by the Brooklyn Visitations after making a name for himself on the playgrounds. He continued the trend in the American Basketball League. He led the league in scoring, and helped Brooklyn win the 1934-35 ABL championship against the dominant Philadelphia Sphas in their prime. He spent a year in the New York Professional League where he set a playoff record for most points with 32. He played with the recently reorganized Original Celtics for the next three years.