Banega is actually an excellent midfielder. He can dictate play and release passes at the right time. He is a true playmaker. The reason he is talked about less is that most attention has been on on Messi, Aguero, Higuain and Tevez when he was still in the national team. Pastors is a good alternative as a playmaker. His problem is playing at PSG, where Emery has been tinkering with the team and decided to use a 4-3-3 with Rabiot, Veratti and Draxler or Lo Celso.
Like I said before, Argentina has problems with player relationships. Tevez is said to have been left out in 2014 because of his incompatibility with Messi, especially with respect to the zones they occupy on the pitch. Dybala was initially left out of the team for the same reasons this year, but Sampaoili changed his mind after some former players conplained.
For the national team you only need a few weeks of preparation because players rarely play together. The coach simply needs to play the players in their proper positions and motivate them. Argentina has always been Argentina and are always considered among the favorites. They can not run away from that.
If you look at the current Brazilian midfield, you have Casemiro, who is a hard nosed competitior, without much skill, but he does his job well as a holding midfielder. Paulinho is similar but more mature and more tidy. Coutinho is the creative force in the middle and is well protected by the other two. I would not call that a star studded midfield. Argentina could have done the same with Biglia, Mascheranno and Banega/Pastore.
