Barcelona can say that they have two players for nearly every position. But in some positions, there are even more players than that.
De Jong, Sergi Roberto, Sergio Busquets, Rakitic, Arturo Vidal, Arthur and Aleña. You could even add Riqui Puig, currently with Barça B, to those seven. This season, it seems impossible, though, that he will get many chances. Ernesto Valverde has a lot of players for three midfield positions and excessive rotations have never worked for the coach.
The key to the overbooking is Sergi Roberto's return to midfield, freeing up the right-back spot for Nelson Semedo, who is backed up by Moussa Wague.
Lately, the player to miss out has been Carles Aleña, which is slightly surprising given he started the first week of the season at Athletic Bilbao. In that game, the players not called up were Arthur Melo and Arturo Vidal, who had a shorter preseason than the rest.
The preferred 'trident' so far seems to be Sergi Roberto, Sergio Busquets and Frenkie de Jong. They have started the last two games together.
Luckily, Barça have managed to get rid of some of their other midfielders this summer: Andre Gomes, Denis Suarez and Rafinha have all sealed moves.