*Club domestic league appearances and goals, correct as of 21 November 2024 ‡ National team caps and goals, correct as of 19:29, 17 November 2020 (UTC)
In June 2016, Morcillo joined Athletic Bilbao at the age of 17,[4] being initially assigned to the farm team also in the regional fourth division.[2] Promoted to the reserves in June 2018,[5] he made his Segunda División B debut for them on 25 August of that year, playing the last four minutes of a 2–0 home win over CD Tudelano.[6]
Morcillo scored his first goal for the B side on 25 November 2018, opening the 1–1 draw at Barakaldo CF.[7] He emerged as an important player during the 2019–20 season by contributing ten goals,[3] including one from the halfway line in a 3–0 away victory against Tudelano on 22 September 2019.[8]
On 8 May 2020, Morcillo renewed his contract with the Lions until 2023,[9] being subsequently called up to pre-season with the main squad.[10] He made his first-team – and La Liga – debut on 12 September, three days before his 22nd birthday, playing the full 90 minutes of a 2–0 away defeat to Granada CF.[11] He was definitely promoted to the first team in October, being given the number 2 jersey.[12]
On 28 April 2021, Morcillo scored his first league goal, in a 2–2 draw at home to Real Valladolid.[17] The following January he was loaned to that side, now playing in the Segunda División, until the end of the season.[18]
On 23 August 2023, Morcillo returned to his first club Amorebieta on loan for the 2023–24 campaign.[19]
^Zubieta, Jon (30 May 2018). "El Bilbao Athletic tira del Basconia" [Bilbao Athletic resort to Basconia]. Mundo Deportivo (in Spanish). Retrieved 12 September 2020.
