In the summer of 2009, he was selected by the manager of FC Barcelona B, Luis Enrique, to form part of the second team Blaugrana.Subsequently, Josep Guardiola called him up to the first team during pre-season in England and the tour in the United States.On 15 August 2009, dos Santos was called up for his first official game with the first team in the Supercopa de España against Athletic Bilbao, although he was eventually ruled out and saw the game as a spectator.^[ He made his debut with Barcelona Atlètic on 5 September 2009 against Mallorca B. The match finished in a 1–1 dra^] dos Santos made his debut for Barcelona on 28 October 2009, coming on as a substitute for Seydou Keita in the 80th minute in an away Copa del Rey match against Cultural Leonesa, which Barcelona won by 2–0.^[ He made his Champions League debut for Barcelona on 24 November 2009 against Internazionale in a 2–0 win at the Camp Nou when he replaced Andrés Iniesta in the 92nd minute. Due to the lengthy 2009-2010 season many Barcelona players were given breaks towards the end of the year. This meant the first team was going to be a few men short, and hence four Barça B players were called up by Josep Guardiola on 29 December 2009. Among these four were dos Santos, Thiago Alcântara, Gai Assulin and Víctor Vázquez^]His La Liga debut came on 2 January 2010 when he started against Villarreal CF before being substituted by Andrés Iniesta in the 60th minute.