Sergio Conceicao says Porto are confident they can mount a storming fightback and knock Chelsea out of the Champions League.
The Primeira Liga champions have a mountain to climb in the quarter-final at Stamford Bridge on Tuesday after suffering a 2-0 home defeat in the first leg last week.
Porto have won only one of their 20 knockout stage matches on their travels and that was back in 2004 against Deportivo de La Coruna at the semi-final stage.
Conceicao warned Chelsea that his side are ready to roll up their sleeves and seal a place in the last four.
"There are many moments overs the years that can be examples of overcoming and believing," said the Porto head coach.
"We are confident. We know that we are going to face a difficult obstacle, but we are here to give the answer that we have to give. The feeling of representing this historic club and its DNA is always on the pitch."
Conceicao says Porto will not go out all guns blazing in London.
He added: "We have to be a compact, cohesive team. It is necessary to score goals, but also not to suffer.
"In the first leg we played a good game, but it was not good enough. If it were, we would have won the game. We will try to improve even more what was a good performance by the team.
"Over 90 minutes for FC Porto it requires the ability to believe and be resilient. We always try to enter with that spirit. We are ready to go to the fight and to fight."