Ascacibar and/or Battaglia should've been given a chance in these friendlies. You won't win the World Cup with any of them in midfield (although Ascacibar is frighteningly talented, such a smart player) but at least not play the old dross that is nowhere near good enough anymore; Mascherano and Biglia (never was really). They aren't strong, they aren't quick and their passing/ball handling when pressured is awful.
Full backs as well is a major problem, with that position being ever so influential on a team's play. Bustos is young and talented but it's to soon for him. Tagliafico is ok I guess but not a world beater either.
With this being the likely team to start the first WC game against Iceland, I can't understand how anyone can claim personell is not a problem (compared to the likes of Brazil, Germany, Spain, France, Portugal):
Romero
Mercado/Bustos - Otamendi - Fazio - Tagliafico
Biglia - Banega
Lanzini - Messi - Di María
Agüero