Giannetti debuted professionally for
Vélez Sarsfield in the
2012 Clausura under
Ricardo Gareca's coaching, starting in a 0–2 defeat to
Argentinos Juniors. The defender was part of the squads that won the
2012 Inicial,
2012–13 Superfinal and
2013 Supercopa Argentina, although he did not play any games. Giannetti became a starter for the team during the second half of the
2015 Argentine Primera División season, in which he started in all 15 games. He scored his first professional goal in the 12th fixture of the
2016 Argentine Primera División, a last-minute winner against Argentinos Juniors. On 6 January 2024, Giannetti signed a one-and-a-half-year contract with
Serie A team
Udinese, with an option for a further year. On 13 August 2025, Giannetti moved to
Antalyaspor in Turkey on a two-season deal. ==International career==