Stefanakos was born in Kalamata, on October 19, 1936, to a family that hailed from Mani. He grew up in Piraeus. As a footballer, he was considered - along with Costas Linoxylakis - as the best centre back of his day. He started playing football at Ilisiakos FC before joining Olympiakos. His career at Olympiakos spanned the years 1957 - 1965 during which he won the league title twice (1958 and 1959) and the Cup five times (1958, 1959, 1960, 1963, 1965).
He was capped 8 times by the Greek National Football Team.
Married to actress Martha Karayianni, Stefanakos developed a love for the cinema and the night life which contributed to his decline as a player. A very disappointing performance in the Cup Winners' Cup against West Ham United of England, was to be his last competitive game in Greece. Afterwards, he migrated to South Africa where he played for three years.
He tried his hand at acting and took part in eight films including:
- «Κομήτης Χάλεϊ» (Halley's Comet)
- «Στην πόρτα της κολάσεως» (At the gates of Hell) - 1960
- «Αγαπούλα μου» (My love) - 1960
- «Καραγκούνα» (Karagouna) - 1961
- «Σκότωσα για το παιδί μου» (I murdered for my child) - 1962
- «Ο διαιτητής» (The referee) - 1963
- «Αθήνα ώρα 12» (Athens at 12 o'clock) - 1964