Mattia started off his career in Primera B Metropolitana with Flandria in 2006.[2] Five years later, after three goals in one hundred appearances for the club, Mattia left Flandria to join San Martín of the Argentine Primera División on loan.[2][3] His debut arrived on 26 November 2011 during a 0–3 win away to Olimpo.[1] In June 2013, San Martín signed Mattia permanently.[4] On 4 August, Mattia scored his first club goal versus Aldosivi in Primera B Nacional; following relegation in the previous season.[1] In his first seven seasons, he made one hundred and forty-two appearances and scored four times for San Martín in all competitions.[1]