Playing at his sixth edition of the tournament, Ronaldo ended his long wait for a goal in the knockout rounds as Portugal emerged as a 2-1 victor in Toronto.

But that does not tell the full story of a chaotic game, as the 41-year-old's penalty got Portugal level after Ivan Perisic had opened the scoring for Croatia.

Ronaldo was then surprisingly substituted in the 81st minute, with Roberto Martinez introducing Ruben Neves as an extra midfielder after watching Croatia retake control of the game, and Goncalo Ramos – another substitute – restored Portugal's lead with a 94th-minute header.

There was more drama to come as Josko Gvardiol saw a potential equaliser disallowed in the 15th minute of stoppage-time because of a subjective offside call, with Igor Matanovic said to have got a slight touch on a cross, which meant Mario Pasalic was offside.

A subsequent touch off the back of Portugal's Renato Veiga, which could have reset the phase of play and led to the goal being awarded, was deemed to be unintentional.

That huge call ensured Ronaldo will get at least one more appearance on football's grandest stage, with Portugal heading to Dallas to face Spain on Tuesday (AEST).

Before the game against Croatia, reports circulated that Ronaldo had already decided to call time on his glittering international career whenever Portugal's campaign ends, but he insists he is yet to consider his options.

"The future isn't important right now," Ronaldo said.

"I'll talk about it, I'll have time – after we win or lose – to talk to my family and then make decisions the way I do.

"I don't make decisions on the spur of the moment any more. Now, I take everything calmly. For now, it's about enjoying today."

Spain is the marginal favourite to progress from the Round of 16 tie against Portugal, and Ronaldo knows how tough it will be against the European champion.

"We know Spain have the quality to win the [FIFA] World Cup," the former Real Madrid forward said.

"It's going to be a difficult game like all of them from now on. We know them well. We are going to be ready."