Samuel is Argentina's best defender. How Demechilies and Heinze get games ahead of him is simply beyond me.
Btw, even though Di Maria has probably been Argentina's only spark upfront, he's just been too selfish for my liking, his decision making is questionable too, he just never knows when to release the ball.
That could all be ironed out with experience of course, he is a very talented player and he's still young. But right now, i don't think he is the finished article.