Portugal coach Fernando Santos said he warned many times that North Macedonia could shock Italy and he was proved right when they won their World Cup qualifying playoff semifinal 1-0 in Palermo on Thursday.
North Macedonia will play the Portuguese in Porto on Tuesday after Portugal beat Turkey 3-1, with the winners advancing to this year's World Cup in Qatar.
"We need to show the same respect to North Macedonia that we would to Italy," Santos told a news conference.
"I told you before we could be playing them, those games are not a joke, it's like a final and anything can happen. You have to face it with the focus and concentration that it deserves. A team that goes to Italy and beats the European champions doesn't need introductions."
Portugal survived a nervy finale to move closer to the World Cup, with Turkey's Burak Yilmaz missing a late penalty that could have forced extra time in a game they dominated in front of sold-out Dragao Stadium.
Leading 2-0, Portugal let their opponents back into the match to the annoyance of their coach.
"We can't allow that to happen in a game we had under control, it's a warning for next Tuesday," Santos said.
"Today's game is over and we have to focus on the next rival that will give us the game of their lives for sure. We'll need extra focus playing at home in front of our crowd. The motivation has to be our main goal, going to the World Cup."
After missing out on automatic qualification in November, Portugal would have expected to face Italy in a clash of the two last two European champions.
"We can't think it will be easy against North Macedonia," Matheus Nunes told reporters after scoring the third Portuguese goal against Turkey.
"Now we have to rest and work for the game plan. It's a team that deserves all our respect. They went to Italy and won, you have to have quality to accomplish that."