It took about 30 seconds for the decision to be announced.
With that, the result now gives both of the teams one point, a fair result.
Mexico head into Sunday's clash having drawn 1-1 with the U.S. in their latest World Cup qualifier, although prior to that they earned comfortable victories over Honduras in a qualifying game and Ireland in a friendly, winning 3-0 and 3-1 respectively. It ended; Portugal 2-2 Mexico.
Portugal's next game is on Wednesday at the Spartak Stadium against Russian Federation, while Mexico will face minnows New Zealand later on the same day at the Fisht Olympic Stadium.
Group B has Germany, Chile, Australia and Cameroon.
But for the next two weeks the main thing on the mind of the reigning Ballon d'Or holder is winning more silverware in the eight-nation World Cup warm-up event.
The Gold Cup winners begin their Confederations Cup campaign against the European champions at Kazan Arena, looking to spring a first surprise of the tournament by claiming all three points. So even losing the opening match would still leave either team in good position to advance through. These are the main favorites to win the group, despite the fact that the tournament takes place in Russian Federation.
Portugal twice surrendered the lead against Mexico in their Confederations Cup opener on Sunday but the 2-2 draw was no cause for alarm, according to captain Cristiano Ronaldo.
"A year ago, I said Portugal were going to Euro 2016 to win it".
Portugal has won six of its last seven games, with the only setback coming in a 3-2 loss against Sweden in a friendly in March.
Portugal coach Fernando Santos said it was not the performance he expected from his team. The Portuguese, perhaps overestimating their strength, started with a defeat in the qualifying cycle at the World Cup, but in the following matches more than such mistakes were prevented, having won five victories in a row.
With the game looking like it may end deadlocked at 1-1 defender Cedric popped up in the box to fire home his first global goal via a deflection.