[1] He was promoted to the reserves on 23 June 2014,[2] and made his senior debut on 5 October by coming on as a late substitute for Eneko Capilla in a 1–1 Segunda División B away draw against CD Toledo.

Sangalli scored his first senior goals on 3 October 2015, netting a brace in a 3–3 draw at SD Amorebieta.

A regular starter for the B-side, he renewed his contract until 2019 on 26 May 2017,[3] but missed out the first months of the 2017–18 season due to injuries.

[6] On 5 October 2018, Sangalli scored his first professional goal, netting his team's second in a 3–1 away win against Athletic Bilbao in the Basque derby.

Their paternal grandfather emigrated from Italy to San Sebastian in the mid-20th century and Luca is able to speak some Italian.