After spending his first two seasons as a backup, Fernández started to appear regularly from the 2017 campaign onwards. He scored his first professional goal on 25 March of that year, netting the winner in a 2–1 home defeat of El Tanque Sisley.[3]
On 4 March 2018, Fernández scored a brace in a 3–2 defeat to Defensor Sporting.[4] On 29 July, he scored a hat-trick in a 5–0 away routing of Cerro,[5] and finished the campaign with 11 goals, playing a key part as his side narrowly avoided relegation.
On 12 December 2019, Fernández joined Toluca on a season-long loan.[6] At the end of his loan, Fernández returned to UANL and was later deemed surplus. On 19 December 2021, Fernández sealed a permanent move to Toluca.[7]
Loan to Fluminense
On 4 July 2023, Fernández joined Fluminense on a one-year loan. [8]
Loan to Peñarol
In January 2024, Fernández joined Peñarol on a one-year loan.
^"Entrevista a Leonardo Fernández" [Interview to Leonardo Fernández]. AUF.org.uy (in Spanish). Asociación Uruguaya de Fútbol. Retrieved 3 January 2019.