The runaway Bundesliga leaders travel to Estadio do Dragao on the back of a comfortable 3-0 league win over Eintracht Frankfurt, but Guardiola knows they can expect a much sterner test in Portugal.
"It is a Champions League quarter-final, which means all the teams have a great level of ability," he said.
"Porto are a top team, I am not surprised by their progress. We can't play once if we want to progress, we need to do it in both games.
"In 99 per cent of our games opponents attack us with long balls. Porto are different, they are not just a counter-attacking team, they want to control the game.
"They have a good attack, often switch the ball well and have good qualities in one-on-one situations. They have good defensive stability and individual quality.
"He [Porto coach Jule Lopetegui] has done a very good job, his team play very good football. We need to be excellent in attack and defence [to progress]."
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