Sergio Ismael Díaz Velázquez (born 5 March 1998) is a Paraguayan professional footballer who plays as a forward for Greek Super League club Panetolikos.

Díaz ranked number one in a list of the most expensive players in Paraguayan football for 2015 published by Diario Extra.

[5] Diaz debuted as a 15-year-old in the Primera División Paraguaya, on 27 June 2014, in a 2–1 home victory against Club General Díaz.

[10] In Diaz's debut for Cerro Porteño in the 2015 Primera División Paraguaya season, he scored one goal in his side's 3–0 away victory against Sportivo Luqueño on 14 February 2015.

[12] Diaz was included in Real Madrid U19 squad for UEFA Youth League, making his debut against Sporting Club de Portugal.

Sergio is a self-proclaimed fan of the English football club Arsenal, which he in May 2015 described as his dream destination in the future.