Chelsea have the belief to deny Barcelona a place in the Champions League final, according to former Blues striker Eidur Gudjohnsen.
Gudjohnsen, 33, who also played for Barcelona, says Roberto di Matteo's side can cling on to their 1-0 lead in Tuesday's second leg at the Nou Camp.
"Chelsea have given themselves great hope by the way they defended at Stamford Bridge," said Gudjohnsen.
"They rode their luck a little bit but they believe they can win."
But, on home turf in the cauldron of the Nou Camp, Barcelona are a formidable proposition though they will need to recover from Saturday's 2-1 home defeat to Real, which saw Jose Mourinho's side go seven points clear of Barcelona with four La Liga matches remaining.
Gudjohnsen believes that if Chelsea can replicate their tactical approach from the first leg they have a chance.
"At Stamford Bridge they were very tactically organised," he added. "They limited the space for Barcelona to play in.
"They will need to do that for 90 minutes in the Nou Camp. It is a very difficult task but they have done it once."
The Spanish champions were unbeaten at home this season prior to Saturday, having won 27 of their 30 matches scoring 105 goals and conceding just 18.
However, Barcelona have not beaten Chelsea in the past six meetings between the sides, a record that dates back to 2006.
The atmosphere at the Nou Camp, where a crowd of 99,000 is expected on Tuesday, is likely to be a factor, according to Gudjohnsen. He made more than 70 appearances for Barcelona and believes the intensity of the passionate Catalan crowd will only add to the occasion.
"They are magical nights," he said. "The crowd really gets behind the team for occasions like that. They can be a very demanding crowd, especially in the league, they want to be entertained. But, when they know the team needs them, they really get behind the players. It will be a great spectacle."
Chelsea's fortunes have been transformed since Di Matteo took over following Andre Villas-Boas's dismissal in March. As well as reaching the FA Cup final with a 5-1 victory over Tottenham Hotspur, Chelsea have revived their hopes of finishing in the top four in the Premier League table.
Gudjohnsen believes Di Matteo has done enough to be given the job on a permanent basis.
When asked if the Italian could take the post on full-time, the AEK Athens striker said: "I think he has shown that he can. He has already turned the season around, they are still looking for that fourth spot in the league.
"He has got them into an FA Cup final and a Champions League semi-final. For the moment everything has gone fantastically well.
"He has made some bold decisions and they are working in his favour. He is doing the job the way he thinks is right and it looks to be going great."