Sweating on the fitness of talisman Ronaldo with the Brazil showpiece just six days away, Portugal could only draw 0-0 with Greece last weekend and were hanging on for another goalless stalemate.
But deep into injury time, up popped stand-in skipper Bruno Alves with a thumping header to seal a victory Portugal barely deserved.
Manchester United winger Nani had been anonymous, while gangly forward Eder failed to convince, leaving Bento with plenty to ponder ahead of Tuesday’s final warm-up match with the Republic of Ireland.
Bento had no fresh update on the fate of his star forward Ronaldo, who has now missed the last two games with knee and thigh injuries that are threatening to wreck his — and his country’s — World Cup.
Bento on Thursday refused to say when the Real Madrid man would return.
“We struggled, mainly at the beginning, with Mexico’s attacks,” said Bento, whose side face Germany in their World Cup opener on June 16, followed by USA and Ghana in a very competitive Group G.
“It’s going to be a balanced group with four strong teams so it’s going to be very difficult for us, but we will fight to the end to achieve our first goal, which is to reach the knockout phase,” said Bento.
“We still have a few mistakes that we need to correct before the World Cup,” he added.
Mexico, playing their last friendly before heading to Brazil, have their problems too.
They dropped striker Javier Hernandez after he failed to fire in a 1-0 defeat to Bosnia on Tuesday, but neither Giovani Dos Santos nor Oribe Peralta did enough to suggest they can trouble the hosts on June 17.
Coach Miguel Herrera was upbeat despite a second narrow defeat on the bounce.
“Even if you lose this way, it’s only a friendly,” he said.
“We have a week to analyze where we failed and where we need to adjust. We need to focus on better results but I like what I’m seeing and how the team is functioning.
“The goalkeeping tonight from Portugal was amazing and if we could have scored it would have been an almost perfect game.”
Mexico enjoyed the better of the openings to both halves and had the ball in the net after just two minutes, but Hector Moreno was ruled offside after prodding the ball in.
Portugal responded when Vieirinha had their first shot on target in the 14th minute, Mexico keeper Jesus Corona turning the ball round his near post.
As well as Ronaldo, the Portuguese were also missing through injury key defender Pepe and experienced midfielder Raul Meireles.
Yet they began to dominate in front of the 56,000 crowd at the impressive Foxborough home of the NFL’s New England Patriots, Eder drawing another save from Corona with a first-time snapshot.
The chances began stacking up in the second half: Corona was quickly down to his near post to deny Fabio Coentrao, while Andres Guardado flashed the ball just wide for the Mexicans as they finished the stronger.
Hector Herrera might have grabbed a winner for Mexico but Eduardo dived to his right and then saved from substitute Alan Pulido with two minutes left to keep the fast-fading Portuguese in the game, before Alves made his late intervention.
As well as hosts Brazil, Mexico face Cameroon and Croatia in World Cup Group A.
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