Coombs Our games actually mattered...to you...me...Arsenal.
They mattered no more or less than the Senegal game did to a Brazilian fan/Ancelotti/Brazil.
It might look like a meaningless friendly, but for a team hoping to win a World Cup these games are effectively like their pre-seasons where they stake their claims, develop their tactics, work on their chemistry and so on. They aren't meaningless, regardless of anyone's opinion of the importance of International football.
It was absolutely predictable that he would be used by Brazil, and I've no doubt Arteta would likely have known exactly how much he was planned to play. With that in mind Arteta's own use of him does come into question.
The same questions about the management of his game time would be asked if he had got injured at Sunderland or Spurs instead of away with Brazil.