Ronaldo won a Portugal record 128th cap in Saturday's goalless draw against the Austrians, a match which will be remembered for his penalty miss when he hit the post late in the second half.
It has been a frustrating tournament for Ronaldo and Portugal, who have failed to win either of their first two group matches.
They must beat Hungary, who are top of the pool with four points, to be sure of reaching the last 16 after drawing with both Iceland and Austria.
Ronaldo is still waiting for his opening goal in France to become the first player to score at four European Championship finals.
The 31-year-old has yet to hit the net, despite launching 20 shots so far, but Portugal coach Fernando Santos has unshakable faith in the Real Madrid star.
"Cristiano will keep on taking our free-kicks and penalties," insisted the 61-year-old.
"We love him, the whole of Portugal loves him.
"We have someone who is the standard bearer for our country, he's like any other amazing figure.
"He will give his best to produce a good performance."
Portuguese journalists pointed to Ronaldo's less-than-positive body language in training as a sign that all was not well with their star, something Santos dismissed.
"The day after the first match, you said he was all smiles, now the story is he isn't smiling," said Santos.
"I'm sure he'll get over that and he will do what he does best -- and that's score goals."
Santos said the only injury doubts are over defender Raphael Guerreiro and midfielder Andre Gomes as he decides which team to select against Hungary.