Chelsea’s 1-0 win would be cancelled out by four of the five home results this season.
In 2002, Panathinaikos suffered exactly the same fate that Barça will need to repeat on Tuesday.
Chelsea have already lost one Champions League semi final after winning the first leg 1-0.
Although 1-0 is by no means an unusual score, this is only the second time in Champions League history that FC Barcelona have been faced with the task of turning around a 1-0 first leg defeat at the Camp Nou. The other occasion was in the quarter finals way back in 2001/02, when Panathinaikos scored the only goal of the first leg in Greece. Managed at the time by Carles Rexach, Barça won 3-1 at the Camp Nou thanks to goals from Luis Enrique (2) and Saviola. And that was even despite Panathinaikos scoring the first goal of the night, which meant Barça needed to score three. Which they did.
It is also impossible to forget the dramatic comeback against Chelsea in the 1999/00 season, after Barça had lost the first leg 3-1 at Stamford Bridge. They eventually qualified thanks to a 5-1 win after extra time at the Camp Nou.
There are also reasons for the Premiership club to feel pessimistic about their chances. In the semi final of this competition in 2006/07, Chelsea got off to a 1-0 start against Liverpool, but then lost by the same score at Anfield. It all came down to a penalty shootout, and it was Liverpool that ultimately won a ticket to the final. (via FCBarcelona.com)