Koumantarakis started out at
South African team
AmaZulu F.C. in 1992. He left the club after six months, however, to join
Manning Rangers where he won the South African title. He joined one of South Africa's most successful teams,
Supersport United FC, in 1996 for a then record South African club to club transfer. He was a success at Supersport and his big move to
Europe came in 1998 when he signed for
Swiss club
FC Luzern. He had a good debut European season in Luzern and did enough to impress
FC Basel. Koumantarakis joined Basel's first team for their
1999–2000 season under new head coach
Christian Gross. After playing one test match, he played his debut for his new club in the home game in the
Stadion Schützenmatte on 26 June 1999 as Basel beat
Korotan 6–0 in return leg of the first round of the
1999 UI Cup and advanced to the next round. He scored his first goal for his new club in the same game. In fact he scored four of the six goals in that game. After playing in another UIC and another test game Koumantarakis played his domestic league debut for the club in the away game in the
Cornaredo on 7 July 1999 as Basel played a 1–1 draw against
Lugano. Koumantarakis scored his first domestic league goal for his new club on 5 August in the away game in the
Charmilles Stadium,
Geneva as Basel played a 1–1 draw against
Servette. He spent three and a half seasons with Basel and during this time Koumantarakis played a total of 130 games for Basel scoring a total of 51 goals. 84 of these games were in the
Nationalliga A, 7 in the
Swiss Cup, 3 in the
Champions League, 5 in the
UEFA cup,
UI Cup and 23 were friendly games. He scored 26 goals in the domestic league, 6 in the cup, 10 in the european competitions and the other 9 were scored during the test games. His period at Basel was undoubtedly the best of his career, winning national titles and playing in European competitions culminating in him appearing in the champions league in 2002–03 season. Basel went on to the final group phase of the competition that year. A move to
England was on the cards next for Koumantarakis, signing for
Championship outfit
Preston North End in January 2003. He was a big signing for Preston but failed to live up to expectations as he was injured on international duty. He left Preston for
German club
Rot-Weiß Erfurt in the 2004–05 season but his time there was plagued by injury and only played a handful of games. Erfurt released Koumantarakis at the end of the season and he signed for
SpVgg Greuther Fürth. He retired without playing a game for Fürth after failing to overcome his persistent knee injury. ==International career==