Muller and Co. were stunned 3-1 in Portugal last week but can advance with a 2-0 triumph at home on Tuesday, prompting the 25-year-old attacker to claim Bayern hardly need a miracle at the Allianz Arena.
But while Muller promised Bayern will give their all to reach the final-four of the Champions League, he warned they cannot afford to ignore their defensive duties.
"It's important we don't get too wound up about the match," he told Bayern's website on Monday.
"Everyone just piling forward would be suicide."
Muller added: "We'll throw everything we've got at it.
"A 2-0 home win for FC Bayern wouldn't be a footballing wonder of the world, but we have to earn the result in the first place."
Bayern conceded twice in the opening 10 minutes in Porto and although Thiago Alcantara pulled a goal back in the first half, the home side wrapped up the match through Jackson Martinez just after the hour mark.
All three of Porto's goals came from Bayern errors with central defenders Jerome Boateng and Dante producing horrible performances.
"We have our backs to the wall to a certain extent," Muller said.
"It was simply damned unlucky timing that we made mistakes in the first leg of a knockout match in the Champions League."
