Fernandez joined Stevenage at the age of 13 and progressed through the club's youth system.[3] Following Ben Wilmot's inclusion in the Stevenage first-team; Fernandez, who was still playing regularly for the club's under-16 team at the time, was called up to play at centre-back in the FA Youth Cup against Middlesbrough's under-18 team.[4] He played 90 minutes of the match, which Stevenage lost 2–1.[5] Stevenage head of academy coach Stephen Payne stated he felt Fernandez's late inclusion and ability to deal with the "pressure environment" put Fernandez in good stead for his professional career.[4]
Whilst a second-year scholar, aged 17,[3] Fernandez made his first-team debut in Stevenage's 2–1 home defeat to Southend United in the EFL Cup on 13 August 2019, playing the whole match.[6] After the match, he was singled out for praise by manager Dino Maamria, who described Fernandez's debut as being "a Man of the Match performance".[3] Fernandez signed his first professional contract on 28 August 2019.[7] He made eight first-team appearances during the 2019–20 season.[8]
Loan spells
Having made one first-team appearance for Stevenage during the opening month of the 2020–21 season,[9] Fernandez joined National League South club Oxford City on a three-month loan agreement on 9 October 2020.[10] He made his debut as a 60th-minute substitute in Oxford City's 1–1 away draw with Chelmsford City on 10 October 2020.[11] He played regularly during his time on loan at Oxford City,[2] making 11 appearances in all competitions.[2] Fernandez was recalled by Stevenage on 24 December 2020 following a number of injuries and suspensions within the first-team squad.[12] He rejoined Oxford City on 21 January 2021, on a loan contract for the remainder of the 2020–21 season.[13] He made three further appearances before the National League South season was curtailed due to restrictions associated with the COVID-19 pandemic on 24 February 2021.[2][14] Fernandez remained at Oxford City until the conclusion of their FA Trophy campaign, losing at the quarter-final stage to Notts County on 27 February 2021.[2]