Porto travel to Chelsea for the second leg of their Champions League tie on Tuesday, with the scores tied at 1-1.
But what chance do Porto have of upsetting the odds and defeating Jose Mourinho's expensively assembled team?
Luis Octavio Costa, a football writer with Portuguese newspaper Publico, explains how Porto will attempt to pull off a shock result.
SELECT THE RIGHT TEAM
Porto always line up the same way - and that is 4-3-3.
They had one game earlier in the season when they adopted a 4-4-2 system but that was only because of injury problems.
The 4-3-3 formation normally means Helder Postiga up front, with Ricardo Quaresma and Lisandro Lopez.
Postiga has had few goals to celebrate in recent months
Although they don't change their way of playing there is a question mark over whether Postiga will be selected.
Postiga remains the top scorer in the Portuguese league, with 10 goals, but has not found the net since December.
Porto defeated Beira-Mar 5-0 on 25 February but Postiga was substituted very early on with the score at 1-0. The goals flowed after that.
Brazilian striker Adriano was expected to leave the club in December.
He went home during the winter break and nobody thought he would return but Postiga's poor form meant that he remained at the club and Adriano has scored in his last three league games.
SOLID AT THE BACK - A HANDFUL UP FRONT
Quaresma is the most important player at Porto.
He has the capability to do something magical and unpredictable.
If Porto emerge victorious from Stamford Bridge I would not be in the least surprised if it was Quaresma who had made something special happen.
Quaresma has been in superb form for Porto this season
He has the same agent - Jorge Mendes - as the likes of Jose Mourinho and Deco.
Regardless of what happens with Porto in the Champions League, I expect him to leave the club in the summer.
Kepler Laveran Lima Ferreira, who is known as Pepe, and Bruno Alves have a strong partnership in defence.
Pepe used to be known as a player who always made one significant mistake in every match.
Sometimes it led to a goal, sometimes it didn't, but there always seemed to be a moment when he would make a big error.
Now his decision-making is a lot more assured - rather like Ricardo Carvalho's when he was at Porto.
Pepe was born in Brazil but is now a Portuguese citizen and I expect him to be called into the national squad.
Alves is learning a lot. He was very aggressive at one point but has calmed down.
The goalkeeper, Helton, has been in good form this season and has been rewarded with several call-ups to the Brazilian squad. He made his debut for Brazil in their friendly against Switzerland in November.
LIFE AFTER MOURINHO
Jose Mourinho is still a hero in Porto - you could see that during the first leg.
There was no booing or whistling as he walked to the dug-out. He is the coach that they still love.
Mourinho is not forgotten but people now recognise that his era is over.
Ferreira has been a stabilising influence at the club
When he left the club it was very difficult - not only because he moved on but because important players left as well.
It is not easy for any team to change coach and players.
Porto had three coaches in the year after Mourinho left, then had a very difficult season under Co Adriaanse.
The club won the league and cup with Adriaanse in charge but his relationship with the board was tricky and he left last August.
Porto seem more stable under Jesualdo Ferreira.
Although he is Portuguese he is nothing like Mourinho.
He is extremely low profile but the players like him and he has their respect. That is very important.
WILL PORTO GO THROUGH?
I think supporters are more optimistic about the second leg than they were before the first leg in Porto.
People have taken encouragement from Porto's performance and the fact that they did not lose at Estadio do Dragao.
Even so Chelsea are very strong at home and historically Porto have struggled in England.
Mourinho remains a popular figure with the Porto fans
Their only positive result was the draw against Manchester United at Old Trafford when Mourinho was in charge.
The way Chelsea played in the first leg reminded me of his Porto team.
Mourinho is very pragmatic and knew that a draw in Porto would probably be enough for his team to go through after the tie at Stamford Bridge.
Porto are not helped by the fact that their brilliant 18-year-old Brazilian, Anderson, is injured.
He was in fantastic form earlier in the season but was injured during a match against arch rivals Benfica at the end of last October and has been out for some time.
I think that Porto perhaps have a 20% of going through from the tie.