Brazil failed to impress in Fortaleza on Tuesday as the hosts and favourites to lift the World Cup were held to a 0-0 draw by Mexico.
Having won their opening fixtures last week, both sides came into the clash knowing a win would all but assure them of a place in the second round.
Unlike much of the action previously seen at the finals, what followed was a disjointed affair devoid of any real pattern, although the hosts created the clearer goalscoring opportunities.
Mexico goalkeeper Guillermo Ochoa put in an excellent display and made a superb save in each half, scooping Neymar's header away following a pinpoint Dani Alves cross in the first period before keeping out Thiago Silva's free header five yards out with just three minutes remaining.
Brazil dominated the latter stages, but ultimately Luiz Felipe Scolari's side failed to deliver the goal the home crowd so desperately craved, and the stalemate leaves the two teams locked on four points at the top of the group.
Cameroon and Croatia meet in Group A's next game on Wednesday, with each knowing defeat would see them exit the tournament.
Brazil made one alteration to the side that defeated Croatia in the opening match, Ramires coming in for the injured Hulk, while Mexico were unchanged from their win over Cameroon.
After a slow start to proceedings, Mexico's Hector Herrera had the first meaningful effort in the 24th minute. Julio Cesar tipped a rasping 25-yard drive over the crossbar, although the officials failed to see the touch and awarded a goal-kick to the hosts.
Brazil's response was immediate, Neymar rising highest to head Alves' cross towards goal, but Ochoa flew to his right to brilliantly claw the effort away.