Roberto Di Matteo believes Chelsea will need to play two "perfect" games to beat Barcelona in their Champions League semi-final.
Former Blues midfielder Di Matteo has sparked a Chelsea revival since being appointed interim manager six weeks ago after the London club sacked Andre Villas-Boas and last weekend he oversaw a 5-1 FA Cup semi-final victory over capital rivals Tottenham Hotspur at Wembley.
But the 41-year-old predicted Chelsea would have to raise their game still further against reigning European champions Barcelona, already regarded as one of the best club sides of all-time.
The first leg of their semi-final takes place at Stamford Bridge on Wednesday and Di Matteo said: "It's fair to say we need two perfect games.
"But I think, also, that the fact we've been performing very well in the last six weeks gives us the belief we can produce two perfect games in this match.
"It's the biggest challenge for any manager to play against the best team in the world, but for every player as well, to be able to compare themselves against one of the top teams in the world."
Meanwhile, Chelsea midfielder Frank Lampard said it was vital the Blues maintained their discipline, as all three of Chelsea's defeats in 10 matches against Barcelona since 2000 have come when they have had a player sent off.
"Discipline is a huge fact at this level," said Lampard. "To play a man down against Barcelona is very tough.
"We have to tackle and close space, but we've got a good discipline in our team. Keeping 11 on the pitch is crucial.
"I think it's imperative to play a pressing game.
"There's no way you can be passive against them, whether you push or defend deep. We'll have a game plan to attack them and it's important to have a sense of urgency in your defenders.
"If you give Xavi and Iniesta time they'll hurt you. We have to pressure them in all areas of the pitch."
Unlike Barcelona, Chelsea have never won the Champions League or its predecessor, the European Cup, although they were beaten in a heart-breaking penalty shoot-out by Premier League rivals Manchester United in the 2008 final in Moscow.
"It's disappointing to have reached so many semis and a final and not won it," said the 33-year-old Lampard.
"It is the greatest competition in world football.
"Some of my worst moments in football have been losing semi-finals, the Barcelona game probably more than ever given the circumstances.
"But you have to take it and bounce back. We hope the Champions League will one day come to us and we'll win it.
"We're under no illusions as to how hard it will be," he added.
"But I like the tag of being underdogs. It's always refreshing if you believe in yourself, and we believe in ourselves.
"You don't want to take too much fear into the game. You can talk yourself into fear by talking Barcelona up.
"You have to concentrate on your own game and be at your best, and if we do that we'll have a chance. We'll have to be at our best, because we're taking on the best."
Chelsea defender David Luiz will miss both Wednesday's match and next week's second leg at Camp Nou with a hamstring injury suffered against Tottenham.
"It's a big loss for us," di Matteo said. "He's a fantastic centre-half who was in good form."