Roberto Di Matteo admits Chelsea have no margin for error if they are to win their Champions League semi-final against Barcelona.
Despite their recent revival in form, losing just one match since Di Matteo took charge, Chelsea are the underdogs in their last-four clash against the defending champions.
Ahead of the first leg at Stamford Bridge, Di Matteo was under no illusions that Chelsea would have to be on top form to have a chance of reaching the final, although he believes the Blues have the confidence to pull off an upset.
"It's fair to say we need two perfect games," Di Matteo said. "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."
With 63 goals this season, Lionel Messi remains a serious threat, but Di Matteo refused to assign one player to mark the Argentine out of the game.
"It has to be a collective team effort and responsibility to stop him," he said. "If you just think about stopping one guy, they've got nine others who can hurt you. The tactic has to be not just to stop one player, but to limit their threat in general rather than just Messi."
He added: "It's going to be a game where we obviously have to make sure we don't concede, but we also have to try and score a goal or two as well if we can to go into that second leg with a good result."
Midfielder Frank Lampard admitted Chelsea's hopes of victory could lie with keeping 11 men on the field. The Blues' three defeats to Barca in the 10 encounters since 2000 have all been suffered after they had someone sent off.
Lampard, who played in two of those losses, acknowledged Chelsea could ill afford to lose a player tonight or in Tuesday's second leg if they were going to shock the European champions.
"Discipline is a huge fact at this level," he said. "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."