On 2 June 2017, Nuñez was called up to the main squad for the pre-season by new first team manager José Ángel Ziganda.[3] He made his first team – and La Liga – debut on 20 August, starting in a 0–0 home draw against Getafe CF.[4] On 30 October 2017, after already becoming a regular starter, Nuñez renewed his contract until 2023, with a €30 million buyout clause.[5] The following 31 March he scored his first goal in the main category, netting the opener in a 1–1 home draw against RC Celta de Vigo.[6]
After making 36 appearances in 2017–18, Nuñez played far less (14 matches) during the 2018–19 season, initially finding himself behind rookie Peru Nolaskoain as well as Iñigo Martínez and Yeray Álvarez in the queue for selection in the position.[1][7]
In November 2020 he signed an extended contract running to 2025, with no buyout clause.[8] During that period he played frequently due to injuries suffered by teammates and when a system with three central defenders was used, but he again found himself to the bench when all were fit and the preferred formation reverted to a central pair; there was even more competition for a place after Daniel Vivian also joined the squad.[9]
On 16 July 2022, Nuñez was loaned to fellow top tier side Celta de Vigo for the season.[10] He featured regularly and impressively for Celta, who took up the option to extend the deal for a second season.[11]
In March 2024, Celta agreed to buy Nuñez permanently from Athletic, for a rumoured fee of around € 10 million, effective in July.[12] On 28 August, however, he returned to Athletic on loan for the season.[13]
International career
On 25 August 2017, Nuñez received his first call-up to the Spain under-21 squad.[14] He was called up to the full side by manager Robert Moreno on 30 August 2019, for two UEFA Euro 2020 qualifying matches against Romania and the Faroe Islands.[15] He made his debut in the second fixture in Gijon on 8 September, coming on as a late substitute for Sergio Ramos with Spain 2–0 ahead; the final result was 4–0.[16] Good club form for Celta Vigo took him back into consideration for selection in March 2023[11] (this was shortly before to Robin Le Normand obtained Spanish nationality and became established in the national side).
He has also played for the unofficial Basque Country team, making his debut against Costa Rica in November 2020 and scoring the winning goal with a header in the closing minutes.[17]
Personal life
Nuñez's father, Abel, was also a footballer and a defender who mainly represented Barakaldo CF during his career,[18][19] having migrated from Galicia to the Basque region when young.[7] His elder brother Asier played in the same position for local Club Portugalete and JD Somorrostro.[20][21]