Chelsea 2 Liverpool 0: If it is a fine line that separates champions from contenders, then no one walks it with more precision than Hernan Crespo. The Argentinian once more showed the poise of a tightrope walker to stop himself from tumbling into an offside position as he clinched victory with Chelsea's second goal.

The flag was wrongly raised against him a minute later as he netted again and, considering the delicate calibration with which he judges a run, officials must sometimes be tempted to take it on trust that he is exactly where he ought to be.

Even if the striker had to spend much of the afternoon roving and waiting for his moment, he did add distinction to a moderate game. Chelsea will be happy to turn their backs on any debate about the exact level of their performance when they have shown, after three draws in all competitions, they retain the knack of winning on the major occasions.

Jose Mourinho's side, with a first clean sheet in seven fixtures, are now 21 points ahead of third-placed Liverpool and 15 in front of their notional pursuers, Manchester United. The numbers are really important only to those who wish to estimate the date when the retention of the title will be confirmed. The visitors were dishevelled at the close.

The goalkeeper Jose Reina was sent off after an altercation in the 81st minute. He burst from his box to tackle the substitute Eidur Gudjohnsen from behind near the corner flag and the challenge was dangerous even though he made contact with the ball. In the squabble that followed the Spaniard turned back, in response to some comment, and gave Arjen Robben a rather gentle push in the face, the Dutchman keeling over as if assaulted. The behaviour constituted violent conduct and the red card from the referee Alan Wiley was not a surprise.

It was a piece of indiscipline that conveyed the exasperation of a line-up that has a capable air but cannot capitalise on phases of domination.

As in last month's defeat at Old Trafford, the humdrum nature of the Liverpool attackers was a severe limitation. With Robbie Fowler left out while he works on his fitness, imagination and sharpness were scarce. Though Petr Cech pulled off one fine block that denied Steven Gerrard an equaliser in the second half, his principal concern had been a facial cut that demonstrated the character of Liverpool's efforts.

They had no intention of being unsporting, but the players could do no more than set up challenges with the defenders and the goalkeeper when they lacked an elusive striker such as Crespo.

A characteristic episode would see a strapping footballer such as Peter Crouch or Sami Hyypia stretching to skew a header off-target. Those denouements were tormenting for Liverpool since they had outplayed Chelsea in the opening 20 minutes.

Claude Makelele was not disconnecting the visitors' attacks as he would later and the visitors' bank of attacking midfielders got into position to feed off Crouch lay-offs. The much-improved Ricardo Carvalho had to be vigilant to pull off key interventions.

A subdued Chelsea endured and went ahead with a goal that rekindled the debate about Rafael Benitez's preference for zonal marking.

Joe Cole won a corner on the right after 35 minutes and Frank Lampard fired it deep. The ball sailed over Hyypia's head and Carvalho knocked it down so that William Gallas could turn near the six-yard line and finish.

Two minutes later Cole dispossessed Stephen Warnock, who presumed he could turn with the ball. The attacker then shot into the side-netting from an angle, enraging Mourinho, who expected Cole to set up a team-mate with the selfless efficiency demanded of this side.

Chelsea were close to extending their lead in the 43rd minute but Crespo, in an extremely rare lapse, was offside when he capitalised on Reina's fumbling of a John Terry header.

Liverpool believed for a while that they could recover and Gerrard, in the 50th minute, beat Michael Essien and Gallas on the left before his low cross flew through the six-yard box.

Crespo, though, was to end the contest. Jamie Carragher headed out a free-kick and Asier del Horno played a pass into the left of the area for the arch-predator. The angle was difficult and so was the bouncing ball, but the angled first-time shot into the far corner of the net was flawless.

Such technique came as a relief after some eagle-eyed decision-making by the linesman in the first half had threatened to make him the man of the match.