Porto will need to hit top form to advance against five-times champions Bayern Munich on Tuesday despite holding a 3-1 first leg advantage in their Champions League quarter-final, coach Julen Lopetegui said on Monday.
The Spaniard warned Bayern remained lethal even though they were missing several big names including Arjen Robben and David Alaba.
"We have to produce a great performance against one of the greatest teams in the history of Bayern," Lopetegui, whose team are unbeaten in the competition this season, said.
"I am expecting a superb Bayern team, regardless of who they will end up playing and we are prepared for what will happen."
Bayern are also without Javi Martinez and Mehdi Benatia, while winger Franck Ribery looks set to miss the game with a nagging ankle injury.
Germany captain Bastian Schweinsteiger returned to team training on Monday but he is also doubtful to start having been out for weeks with an ankle injury and a subsequent virus.
Bayern are chasing a treble of titles and their fourth straight Champions League semi-final appearance. Twice winners Porto have not reached the last four since winning the trophy in 2004.
Lopetegui had the luxury of resting nine players who had played against Bayern in their 1-0 league win over Academica on Saturday.
"We need to put everything we have planned into practice," said the coach, who was a former Barcelona and Spain team mate of Bayern coach Pep Guardiola.
Porto will be without suspended Danilo and Alex Sandro but Jackson Martinez, who made his comeback from injury against Bayern and scored their third goal and Ricardo Quaresma, who scored the other two, are looking in fine form.
They also have defender Ivan Marcano back from suspension.
"It will be a very difficult task but we will try to find simple answers," Lopetegui said.
"We like the idea of playing Bayern, who are one of the best teams in the world. We cannot think about what could happen, we must focus on the game tomorrow and try to give the answer on the pitch," he said.
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