The 2 new signings could debut against Espanyol
FC Barcelona can register new players until January 2016 due to FIFA's sanction after U18 illegal signings. So despite having brought Arda Turan and Aleix Vidal to Barcelona, the players won't be able to play until next year, when the winter market is open.
This morning the calendar was announced and the first match in 2016 will be against Espanyol, on January 3. So Aleix Vidal and Arda Turan could debut against the opponent of the city.
During the first 5 months of competition, both players will miss matches from 6 competitions. The first big one will be the UEFA Super Cup, which will be played in August 11 against Sevilla, the former team of Aleix Vidal. They will also miss the two matches of the Spanish Supercup and the first round of La Liga's matches vs complicated teams like Real Madrid, Atlético Madrid, Valencia or Sevilla. They will also miss the first Copa matches and the group stage of Champions League. Finally, they will also be absent in the Club World Cup, which is going to be played in Japan (in December).