Mieres began playing rugby at a young age for Lobos, the only rugby team in his birthplace of Punta del Este, Uruguay.[1] Due to his great speed and footwork, as well as a remarkable skill for tackling he was selected to play for the national youth teams throughout every category.
In 2010, he received his first full cap for the first team of Los Teros[2] and then went on to alternate between Los Teros XV's team and the 7's team, depending on each's calendar.
In November 2015, Mieres was tested on a week trial on Coventry Rugby Club, till he finally signed a short contract with the team. The player returned to Lobos in early 2016.