Ronaldo brushed off speculation about his Real Madrid future, although Portugal conceded a late equaliser in a 2-2 draw with Mexico.
Ronaldo teed up Ricardo Quaresma to fire Portugal ahead in the first half in Kazan, but the goal was cancelled out before the break by Mexico striker Javier Hernandez's bullet header.
Cedric Soares restored Portugal's lead on 86 minutes, but Hector Moreno's stoppage-time header salvaged a point for Mexico in their Group A opener.
"We could have killed off the match but it didn't happen. The draw is a fair result without doubt," said Portugal coach Fernando Santos, whose side wore black armbands in honour of the victims of a deadly forest fire back home.
"I would like to say something on behalf of my players. People are very sad in Portugal and the players are thinking of all those who are suffering from what's happened."
Mexico coach Juan Carlos Osorio said his team deserved their point but admitted there was work to be done going forward.
"Hector Moreno's goal handed Mexican football a huge result," he said.
"We still need to work on our finishing, we're not efficient enough in the final third of the pitch.
"The next match will be very tough because New Zealand will give it their all."
Ronaldo, 32, is reportedly furious over a tax probe into the off-shore accounts dealing with his image rights, and has reportedly vowed to leave Spain.
According to Spanish paper Marca on Sunday, Real Madrid's coach Zinedine Zidane even broke off his holiday to call Ronaldo to try to persuade his star not to quit the club.
But Portugal's talisman was at his best in an action-packed first half in his team's opening match, with hosts Russia and New Zealand still to come in the group.
Ronaldo's superb volley looked to have helped Portugal take the lead, but the video assistant referee came to Mexico's rescue after Nani had put the ball in the net.
When Ronaldo's volley thumped the crossbar, Nani pounced on the rebound, but the video ref spotted that four players were offside.
However, Portugal, and Ronaldo, were not to be denied.
The Euro 2016 winners took the lead on 34 minutes when Ronaldo sprinted into the box and his beautifully-timed pass found Quaresma unmarked in the area.
The Besiktas winger drew Mexico's goalkeeper Guillermo Ochoa and tapped home the opening goal.
But Mexico responded with Hernandez testing Portugal keeper Rui Patricio, before putting his side level.
Mexico's all-time top scorer grabbed his 48th international goal from 93 appearances after some dreadful defending by Portugal.
Borussia Dortmund midfielder Raphael Guerreiro failed to deal with a cross into the box and Carlos Vela teed up Hernandez, who met the cross with a diving header.
After an explosive opening period, the second was a much tamer affair as both teams squandered half chances as the tempo dropped.
With time running out, Southampton right-back Cedric pounced on a loose ball and slammed home Portugal's second goal.
But with the 90 minutes up, Mexican defender Moreno rose highest from the final corner of the game to head in the equaliser.