The 21-year-old midfielder made his name as the captain of the silver medal-winning Paraguayan 2004 Olympic football team. He moved from Cerro Porteno to NEC Nijmegen two years ago and made his debut for the Dutch side at FC Groningen in February 2004. He has represented his country at Under-17, Under-20 and Under-23 level and made his senior debut in July 2004. Barreto has a contract with Nijmegen until the end of the 2007-08 campaign.