Liverpool 0 Blackburn 0: If this is, as Rafael Benitez has insisted, the most critical week of Liverpool's season, then it has started wretchedly.

An infuriating stalemate against a disciplined Blackburn side meant another opportunity to eat into Everton's advantage in fourth place has been passed up.

An evening of frustration here was an agonising way to approach Sunday's wildly anticipated 201st Merseyside derby, though triumphing in that fierce contest increasingly appears to be Liverpool's only route back to fourth.

Given the errors which riddled the home side's play, it is best not to contemplate the pressure likely to bite at the weekend.

Everton will have a seven-point lead going into that game. For Benitez, time is ticking inexorably away.

This was a test of Liverpool's patience, an ugly and attritional contest reverberating to the thunderous tackles in a cluttered midfield.

Rovers have been stingy in recent weeks and their rugged suffocation of the home side's attacking intent was admirably implemented again here.

Aaron Mokoena, a destructive influence at their heart, snapped into a succession of challenges with his fellow midfielders ever eager to spring forward on the counter.

Not that many opportunities could be squeezed from the mish-mash. Morten Gamst Pedersen pummelled a free-kick into the wall, though their most presentable first-half opportunity stemmed from a horrendous Jerzy Dudek clearance which was collected by Steven Reid but battered into the Anfield Road end.

The Pole's hesitancy was in keeping with the increasingly edgy tone and Liverpool threatened to profit only on the few occasions they avoided the muddle in the middle.

Benitez had opted to rest one of his more productive wide players, John-Arne Riise, ahead of the derby, though Stephen Warnock, galloping forward from left back, still thrived.

The youngster crossed magnificently into the six-yard box early on to discover, not for the only time, that there was little Liverpudlian presence in the centre to capitalise.

That had the locals chuntering, Luis Garcia's enigmatic performance adding to the frustration. Mauricio Pellegrino, selected ahead of Sami Hyypia, who had apparently been suffering with a stomach bug, skied over the bar from Steven Gerrard's corner and, when Fernando Morientes found rare space in the visitors' box, the excellent Ryan Nelsen leapt in to challenge.

Blackburn Rovers had not lost by more than one goal in their previous 18 games and this display showed why.

David Moyes, watching in the main stand alongside his assistant Alan Irvine, will hope his Everton side are as awkward on Sunday, but he will have recognised Rovers' performance here from that which floored Everton at Goodison Park 10 days previously.

Jon Stead had emerged then to conjure narrow victory, their fourth in seven away games. Liverpool shivered at the prospect of a repeat.

They have lacked the spark required to ignite such occasions at times this season, prompting Riise's belated introduction at the interval, and the Norwegian instantly offered incision down the flank.

He bustled beyond Lucas Neill early and pulled a cross to the top of the area where Milan Baros could only slice his attempt high and wide.

In the circumstances this was no time for profligacy.

Yet, for all their searing form in the Champions League, this is a Liverpool side saddled with an indifferent league record since the turn of the year.

Only three of their previous eight Premiership games had been won, hardly suggesting theirs is a side breathing down Everton's neck in the race for that Champions League spot.

LIVERPOOL: Dudek, Finnan, Pellegrino, Carragher, Warnock (Biscan 82), Luis Garcia, Gerrard, Hamann, Smicer (Riise 45), Baros (Nunez 70), Morientes. Subs Not Used: Hyypia, Carson. Booked: Gerrard.

BLACKBURN: Friedel, Neill, Todd, Nelsen, Johansson (Matteo 62), Mokoena, Emerton, Reid, Flitcroft, Pedersen, Stead (Gallagher 75). Subs Not Used: Enckelman, Tugay, Johnson. Booked: Flitcroft.

Referee: B Knight (Kent).