Juan Carlos Osorio decided to make eight changes from the first game to the game against New Zealand.
The Real Madrid star's strike was his 75th goal for Portugal and the 56th time he has hit the net since the start of last season, with Ronaldo backing his team to follow up their win at Euro 2016 with more glory in Russian Federation.
Portugal also advanced from Group A after beating last-place New Zealand 4-0 in St. Petersburg.
While acknowledging Ronaldo's status, New Zealand manager Anthony Hudson was keen to stress that even without him, the European champions will pose a serious test for his already-eliminated side.
Ronaldo twice threatened the New Zealand goal in quick succession, nodding straight at goalkeeper Stefan Marinovic on 24 minutes and then clattering the crossbar shortly after with another header from a Ricardo Quaresma cross.
"It's an extraordinary scenario because it gives Mexican football and this group of players the possibility of showing that we have the capacity to take on this responsibility, that we have the talent and the determination to play in this scenario".
"We are making steps in the right directions, and I'm convinced of that", he said. On the other New Zealand, a country with one professional team and only a smattering of players at top clubs across the globe.
New Zealand had no business competing with Mexico.
Nani completed the scoring with his 25th worldwide goal. They played admirably against Portugal and probably deserved a point, but now they'll need to be the aggressors.
While Ronaldo is officially the world's best player, Russia's inexperienced backline were badly exposed against Portugal and could come underdone again if they are forced into facing Mexican pressure without any outlet of their own to press forward. We do not think that we will play only against Ronaldo.
"After the game with Mexico, we had mixed feelings".
Ronaldo's eighth-minute header in Moscow gave Portugal their first win in the tournament and victory over New Zealand on Saturday would secure a semi-final spot.
It had been a great start for the Russians, keeping Mexico from creating significant chances and threatening on counterattacks. "On paper they are certainly better than us. We are pleased that we showed a good game but disappointed with the result", Hudson said of the 2-1 loss to Mexico.
Portugal are aware that only one point is needed from this game to guarantee qualification for the semi-finals of the competition. We need a positive result. You were the first to come to Russia's World Cup, after us.