[3][4] In 2008, he played alongside Gai Assulin and Iago Falque in the team that reached the final of the Spanish Youth Cup, in which they lost 2–0 to Sevilla's youngsters.

[5] Recommended by an agent who likened him to Albert Riera, then of Liverpool, Vallès had a week's trial with English Premier League club Birmingham City.

[6] The trial proved successful, and in May 2010, he signed a pre-contract agreement to join the club on 1 July upon the expiry of his contract with NAC Breda, for whom he had played four matches in the Eredivisie.

[11][12] He made a return to the first-team squad as an unused substitute for the final match of the season, which confirmed Birmingham's relegation from the Premier League,[13] and the club took up their option to extend his contract for a further year.

[12] Vallès was occasionally included in the matchday squad during that year but made no more first-team appearances, and he was released when his contract expired at the end of the 2011–12 season.