Pires qualified for the men's 4×200 m freestyle relay, as a member of the Portuguese team, at the 2004 Summer Olympics in Athens. Teaming with Luís Monteiro, Adriano Niz, and João Araújo in heat one, Pires swam an anchor leg in a split of 1:50.71, but the Portuguese team finished the race in seventh place and fourteenth overall with a national record of 7:27.99.