Prieto's first club was General Díaz.[1][2] He made his professional debut at the age of seventeen, featuring for thirty-two minutes of a 2–1 win over Rubio Ñu in the Paraguayan Primera División on 5 September 2014.[1] Over the course of his opening five seasons, Prieto made one hundred and seven appearances in all competitions for the club whilst netting eight times; with his first goal coming in January 2016 against Sportivo Luqueño.[1][3][4] Two years later, having played twice in the 2019 campaign, Prieto completed a loan move to Godoy Cruz of the Argentine Primera División.[5][6]