Ferreyra made his first Argentine team, as a 23-year-old, at the 2000 Summer Olympics in Sydney, competing in two swimming events. In the 100 m breaststroke, Ferreyra rounded out the fifth heat to last place and fifty-third overall by less than 0.19 of a second behind Belarus' Aliaksandr Hukau in 1:05.75. He also placed eighteenth as a member of the Argentine team in the 4 × 100 m medley relay (3:43.61). Teaming with Eduardo Germán Otero, Pablo Martín Abal, and José Meolans, Ferreyra swam a breaststroke leg in a split of 1:02.73.