Chelsea continue their march to The Premiership title with a 2-0 win over Portsmouth at Fratton Park, without ever being at their best on the South Coast.

If championships are won by winning when not at your best, then Chelsea have at least a tentative hand on The Premiership crown.

Their king this season has been Arjen Robben and after he opened the scoring on 78, the points were destined for West London and substitute Joe Cole duly confirmed victory with a second in the final moments.

Mourinho had voiced his concern pre-match over the number of games played over the festive period and in the opening period, his misgivings proved to have some substance.

With Portsmouth snarling into tackles and Fratton Park meeting each thunderous challenge with rapturous applause, Chelsea were a shadow of the side which has had the look of champions in recent weeks.

Amdy Faye and Nigel Quashie were models of controlled aggression in the centre of a congested midfield, that snuffed out the threat of a peripheral Frank Lampard, and on the flanks, Steve Stone and Gary O'Neil combined economy with some neat invention.

Fatigue after Boxing Day exertions against Aston Villa had reduced Eidur Gudjohnsen to a place on the bench and without the Icelander's wit in possession, Damien Duff and Robben looked starved out wide.

Gudjohnsen's place was sacrificed for Didier Drogba's return but after a promising start in which he was denied an opener, the powerful African faded and spent more time berating the match officials than chasing the ball.

It was Chelsea that conjured the first opportunity of a half that saw a dearth of chances, through Drogba, but it was Lampard that was left most perplexed when he saw his goal bound effort blocked from Robben's clever cut back.

Chelsea's superiority in possession would prove short lived, as for the rest of the opening period they were hurried out of the game by Portsmouth's endearing appetite for the fight.

With Claude Makelele, such a vital cog in Chelsea's set-up, troubled by Diomansy Kamara's willingness to drop deep and challenge for possession - the away side failed to find any kind of rhythm and were it not for the agility of Petr Cech, they would have gone into the interval trailing.

For Portsmouth, Quashie is not the type of midfielder shy of taking a shot and when he unleashed the most sumptuous of strikes midway through the half, an unlikely goal of the season contender looked to be in the offing.

However, much of Chelsea's success is built on defence, and it was the excellent Cech that kept the score level when he arched his body to produce a world class stop.

After a bright opening quarter the game then lulled and whilst the contest remained intriguing, opportunities were scant and Mourinho's men returned to the dressing content to be on a level footing.

Chelsea re-entered the field in a determined fashion and for the first ten minutes played with the type of intensity and quality that Mourinho would have urged. With Duff finally engaged in the action, his run cross field run from left to right exposed space behind Portsmouth's backline but when Drogba was slipped in, he could only find the chest of Shaka Hislop.

It would prove Drogba's last contribution and it was his replacement, Gudjohnsen, that spurned the game's best chance when with his back to goal he could only guide the ball over the top from a yard.

Like the first half, Portsmouth were to show their visitors scant regard for reputation and soon found themselves back in the game - albeit without creating genuine opportunities.

Their most noteworthy effort came from substitute Ricardo Fuller, who bent a clever snapshot wide before Gudjohnsen forced a sharp stop from Hislop's feet from close range.

Then came Robben's decisive contribution. A peripheral figure throughout, the dynamic Dutchman received possession from Lampard's poked pass on the right of Portsmouth's box. Cutting onto his left foot, Robben bent an effort that deflected off the knee of Matthew Taylor and past Hislop.

Chelsea never look like conceding a lead and after Robben's opener there was only ever to be one winner and in the final minute, Cole wrapped up the points when he bent a cute effort past Hislop from the edge of the box.