LONDON: Guus Hiddink has warned Chelsea they cannot afford "the slightest error" when they confront Barcelona in this week's Champions League semifinal decider.

The two teams played out a tense goalless draw in the first leg at the Nou Camp and, while Chelsea are widely deemed to be the slight favourites ahead of Wednesday's return at Stamford Bridge, their lack of an away goal means any mistake could prove fatal against the La Liga leaders, who later Saturday went on to trounce arch rivals Real Madrid 6-2.

Chelsea warmed up for the meeting with Barca by beating Fulham 3-1 in Saturday's west London derby here at Stamford Bridge. But Hiddink was concerned at the defensive mistakes which saw the Cottagers cancel out Nicolas Anelka's first-minute opener through Erik Nevland and then create several other chances in the first-half.