Gentile grew up in St. Louis, Missouri where he graduated from Christian Brothers College High School in 1962.
[1] Gentile went on to play for St. Louis University, gaining first team All-American recognition in 1965.
In 2009, Gentile was named to the St. Louis University Men's Soccer Half-Century Team.
[3] In 1967, Gentile signed with the St. Louis Stars of the National Professional Soccer League (NPSL).
He then played three 1970 FIFA World Cup qualification matches, all three wins, the first over Canada and the next two over Bermuda.