However, Argentinian referee Nestor Pitana called for a review from the video assistant referee and it was eventually ruled Pepe was one of four players who were offside from Joao Moutinho's first cross into the box following the failed set-piece.
Another defensive error led to Mexico's equaliser just before the break as Raphael Guerreiro lost sight of Raul Jiminez's cross and Carlos Vela popped the ball back across for Hernandez to head in.
The result puts the sides level on one point each in Group A, behind hosts Russian Federation, who defeated New Zealand 2-0 in their opening game clash in St. Petersburg on Saturday.More news: Change of Prime Minister 'not on the agenda' - Chris Grayling
Both teams are trailing hosts Russian Federation in Group A, who beat New Zealand 2-0 in the tournament opener on Saturday. First, Portugal will take on group leaders Russian Federation in Moscow.
Late dramaJonathan Dos Santos was at his best again for Mexico.
Man-of-the-match awards at major tournaments are not renowned for their originality but it still seemed a questionable move when, amid a chaotic finale to Portugal's 2-2 draw with Mexico, FIFA announced that Cristiano Ronaldo had been voted the game's stand-out player.
Months after the historic success and the total of three appearances in his country's FIFA World Cup qualifying campaign, Quaresma is once again out to prove his worth over and over again at the Confederations Cup in Russian Federation. "[We] try to play football, go on the front [foot], to press, score a lot of goals and thankfully we got one point".More news: Perez rubbishes talk of Manchester United deal for Morata
The respective world rankings, Mexico are 17th and the Kiwi side are 95th, also indicates Anthony Hudson's squad are faced with a stiff task.
Mexicans have the hump with the Real Madrid star as he was caught mouthing "they are very bad" to Pepe during Sunday's Confederations Cup match.
Fernando Santos sent Portugal out in a 4-4-2 formation on the Confederations Cup debut, with talisman and captain Cristiano Ronaldo leading the line alongside Nani but despite their obvious superiority on paper, they struggled to get a hold of the ball in the opening exchanges.
Quaresma switched positions during the match, going from left flank to the right, menacing Mexico along the way, proving that head appears to have finally won the battle over his restless heart.
Portugal ended 2-2 with Mexico and, perhaps fortunately for FIFA, Chile beat Cameroon 2-0.More news: Adele visits London firefighters after tower block blaze
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