The nations won their opening fixtures of the tournament, Brazil coping with the huge weight of home expectation by overcoming Croatia 3-1 in controversial circumstances on Thursday.
Awarded a soft-looking penalty at 1-1 to move in front for the first time in the match, the hosts also saw their opponents have a goal controversially ruled out when Ivica Olic was adjudged to have fouled goalkeeper Julio Cesar.
Mexico, on the other hand, benefited from perseverance on Friday, as Miguel Herrera's men twice saw Giovani dos Santos strikes wrongly disallowed for offside before Oribe Peralta eventually slotted home to earn them a 1-0 win over Cameroon.
Brazil, with Cameroon to come in their final pool game fixture next week, can put themselves in pole position to top Group A with victory in Fortaleza.
Home fans will be hopeful of a more dominant Brazil performance this time around, after Croatia exposed some defensive frailties in Thursday's opener, not least when left-back Marcelo turned the ball into his own net to give Niko Kovac's team a shock lead.
Talisman Neymar, scorer of two goals against Croatia, will be out to continue his fine goalscoring record for his country, and Mexico captain Rafael Marquez - appearing in his fourth finals - has warned of the threat posed by the Barcelona man.
Herrera has no injury problems in his squad, with Mexico aiming for a repeat of the 2012 Olympics final, when they caused a surprise by beating Brazil 2-1 at Wembley with Peralta scoring twice.
