Martínez started his youth football career with Charruitas and joined Nacional later. He was part of Nacional's 2018 U-20 Copa Libertadores winning squad.[2] He made his professional debut for the club on 16 September 2019 in a 4–1 league win against Liverpool Montevideo.[3][4] On 30 August 2021, Brazilian club Red Bull Bragantino announced the signing of Martínez on a five-year deal.[5]
On 31 August 2022, Martínez joined Danish Superliga club Midtjylland on a season long loan deal with a purchase option.[6] On 16 November 2022, he signed a contract until June 2027 with the club after they exercised their option to buy him on a permanent basis.[7]
International career
In June 2023, Martínez received his first call-up to the senior team for friendly matches against Nicaragua and Cuba.[8] He made his debut on 14 June in a 4–1 win against Nicaragua.[9]
In June 2024, Martínez was named in Uruguay's 26-man squad for the 2024 Copa América.[10]