That's pretty apparent for anyone who's watched the 3 Brazil matches. Their defense is completely suspect and Neymar is the only attacker who has really shown up.
It's weird how both Argentina and Brazil are both being led by their superstar, but have suspect defense.
Thiago Silva is all class, but their backs leave a lot of room and their wingers are not helping, plus David Luiz will forget his marking assignments/rush into a tackle when he has no support/pass the ball to an opponent in his own half at one point during a match.
Both Chile and possibly Colombia will be huge tests for this defense. They won't beat them unless they improve or get some serious help by the ref.