In the
2001–02 season, Diamantopoulos led the
European-wide 2nd-tier level FIBA Saporta Cup in scoring,
averaging 22.6 points per game. In the
2002–03 season, he was the
Greek League Top Scorer, while playing for
Panionios. He was also a player of the
Greek League clubs
Papagou and
Olympiacos Piraeus. He was also a member of the
Italian League club
Roseto Basket, and the
Spanish Second Division club
La Palma. In the
2006–07 season, Diamantopoulos won the
FIBA EuroCup Challenge championship, while playing with the
Russian Super League club
CSK VSS Samara. He then played with the
NBA Summer League squad of the
NBA club the
Indiana Pacers. During the 2007–08 season, he was a member of
Kolossos. He joined
Maroussi for the 2008–09 season. He moved to the
Cypriot League club
Achilleas in 2010, and then to the
Swiss League Vacallo Basket in 2012. He also played with the Cypriot club
Keravnos in 2012. He joined
Doxa Lefkadas in 2013. He returned to Panionios in 2014. In 2015, he moved to
Papagou, and to Ermionis in 2016. He retired from playing professional basketball in 2017. ==National team career==