The Ballon d'Or winner continues to struggle for fitness, and despite his stunning cross helping to keep his side in the World Cup, it is a stay of execution.
It took until the very last minute for Ronaldo, almost down and out, to live up to that early excitement and prove his enduring quality on what had been a long and testing night.
His right-wing cross for Silvestre Varela to head home at the death keeps his team alive, for now at least. The pressure placed on his shoulders, inadvertently by his teammates and purposely by the locals here in the Amazon, almost looked too much for him.
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The initial excitement in these parts started to build around six months ago, as soon as the World Cup draw promised to bring the Real Madrid superstar to this oft-forgotten part of the world. This past week that anticipation has reached fever pitch, with around 600 fans camped outside the Quality Inn ahead of their arrival on Friday night, and almost everybody in the city trying to get their hands on spare tickets.
But between the fifth minute and the 93rd, it had been a patchy, cautious performance from the world's best player. It would be remiss, though, to criticize him too harshly. He did about as much as the conditions allowed.
Firstly, his knee is clearly not ready. After showing off his fitness to the press in open training at the Arena da Amazonia on Friday night, you got the impression that he was finally about to arrive at the 2014 World Cup following a poor outing against Germany.
But while he can still produce stunning exhibitions of trickery and speed which 99 percent of the planet could never hope to match, he cannot do the things which have made him arguably the best player in the world. For the vast majority of this match, this was not Ronaldo.
He completely abandoned his position on the left and offered his fullback, first Andre Almeida and then Miguel Veloso, no cover whatsoever. In attack it appeared he was not up to the explosive bursts of pace which have torn teams across Europe to shreds for the past five or six years.
Secondly, his attacking teammates barely offered him anything. Aside from the opening goal, Nani was at his wasteful worst. Eder, an early replacement for the injured Helder Postiga, was too weak and not inventive enough to carve out openings through the middle. This Portugal side without Ronaldo at full tilt have been brutally exposed for how average it truly is.
The defense was dogged - never more so than Ricardo Costa's remarkable goal-line clearance - but eventually it caved in, conceding twice, only to be bailed out once again by the team's captain.
The States, of course, must also take credit for shackling the Ballon d'Or holder. The Americans deserve credit for the attitude, effort, commitment and belief which will characterize their tournament, however far they go.
The midfield and defense barely gave him space in which to work throughout the match, executing a gameplan which has obviously been practiced for months. But as the U.S. fans were dreaming of the last 16, he picked out Varela at the back post to snatch a point with the last action of the game.
This could have been the last we saw of him in Brazil, if reports over the extent of his knee injury are accurate, he may well have been rested for a dead rubber against Ghana. Real Madrid may be cursing their luck that the Seleccao are just about still fighting, and Ronaldo will be at the forefront.
He and his side are still likely heading home early. A point between the States and Germany, coach Jurgen Klinsmann's homeland, will see both teams through.
But for now it is enough for Portugal to fight on, just as Ronaldo had done all night. Plenty of Americans left the stadium in tears, and thousands more locals may well be disappointed they did not see the best of Cristiano Ronaldo. But he did everything in his power.