During his pro club career, he was most notably a member of the Spanish League's FC Barcelona, and the NBA's Philadelphia 76ers.

After that, he began his professional club career at the age of 17, with PAOK Thessaloniki of the Greek League, in the 1993–94 season.

Unfortunately, in August 2006, he announced his retirement from playing pro club basketball at the age of 30, because of injury problems.

Rentzias was named the MVP of the 1995 FIBA Under-19 World Cup, after he helped Greece to win the tournament's gold medal, scoring 33 points and grabbing 21 rebounds in the final against Australia.

Team that featured future NBA players like Vince Carter, Trajan Langdon, Stephon Marbury, and Samaki Walker.

Rentzias was also a member of the senior men's Greek national team, from 1992 to 2003, and with Greece, he competed at the 1996 Atlanta Summer Olympic Games.