Martin Riley was born in Winnipeg and made his first impact in basketball as a student at Sisler High School. In 1973, Riley was the captain of a Spartans squad that finished with a record of 38 wins, 0 losses en route to the provincial championship - the only varsity boys team in Manitoba that had accomplished such a feat to this date. Riley also won the coveted Carl Ridd Award for excellence in academics and on the basketball court.
Riley was the first player to gain a spot on the Canadian National Team right out of high school and he played a major role in the revival of the national basketball program. In 1973, the federal government seriously contemplated termination of the program, but Riley's contribution led to an impressive showing for the Canadian team at the Montreal Olympiad of 1976. Although the team was defeated in the bronze medal match, Canada finished among the top five basketball nations in the world.
In 1976, Riley led the University of Manitoba Bisons to the national championship and was awarded the Mike Moser Trophy as the country's top player. He was selected as Manitoba's Athlete of the Year in 1976 and was named to the All-Canadian team in 1977 and 1978. Riley guided the Nicolett Inn basketball team to consecutive Senior Men's national titles in 1979 and 1980 and was named captain of the Canadian team that did not participate due to the boycott of the 1980 Moscow Olympics. In the early 1980's, Riley played professionally in Argentina for two seasons and ended his playing career with the national program. After his time as a coach with the University of Manitoba from 1981 to 1984, Riley led the basketball programs at Churchill High School and later at Dakota Collegiate.