The Real Madrid forward responded to critics of his early form at Euro 2016 with two goals and an assist in the 3-3 draw with Hungary that secured his side's place in the knockout phase.
And Cacic is eager to restrict Portugal's attempts to get Ronaldo involved in the game when the two sides meet at Stade Bollaert-Delelis in Lens.
"Of course we have to take care and defend well, they're a team with great individuals and of course Ronaldo is their main player," he said. "What we have to do is not allow him to show how strong he is.
"We just have to be focused and make sure they cannot play like they want to play. We have to defend strongly against Ronaldo."
Midfielder Luka Modric and striker Mario Mandzukic missed the 2-1 win over Spain due to muscle problems, though both joined in the open session of training on Friday without any difficulty.
Cacic hopes to have both available but would not reveal whether he expects them to be fit to play the entire game.
"I cannot say if they are fit to play the whole 90 minutes," he said. "Everything looks good but I'll decide tomorrow before the match."
Cacic is adamant there are no favourites for Saturday's game - despite Portugal having yet to record a win at Euro 2016 - but he is confident his side can bring an end to their dismal run against Fernando Santos' side, with Croatia having failed to score a goal in three consecutive defeats.
"It's difficult to say who is the favourite team, you can only say that third place didn't show how Portugal were playing. They had three draws but were really close to winning and have great individuals," he said.
"You cannot say there are easy opponents, especially after the group stages. There were many tight matches and some surprises, it wasn't as most people were expecting.
"Every match is different, every approach and preparation. But of course we have to play our game and show a really good performance.
"They didn't win, it's true, but they'll respect us for sure and try everything to win the game. We have a really bad record against Portugal but we scored some goals, we lost 3-0 in 1996 so we need to change these results. I think my team is ready to do it tomorrow."
"Ivan has played at a top level for the last couple of years. He fits really well," he said. "It's probably the atmosphere in the team - when everything works so well, players can perform at this kind of level."