[1][2] Martegani joined San Lorenzo in 2017 having played as a younger player with his local Club Atlético Argentino de Rojas.
[3] He made his debut for San Lorenzo in the Copa Argentina against Club Sportivo Estudiantes on 22 May 2019.
[4][5] On 11 October 2021 Martegani scored his first league goal with a left footed strike in a 2–1 victory over Club Atlético Colón.
[7] San Lorenzo also reported an offer of €4million came in from Hellas Verona for his services which was rejected as insufficient.
[11] A left-footed playmaker, Martegani has been praised for his dribbling, through balls and ability to shoot from range.