El-Hadji Diouf's header earned a point for Blackburn as Chelsea's title aspirations took a blow at Ewood Park.They had led for much of the game after Nicolas Anelka opened up the injury-hit hosts on the right and pulled back for Didier Drogba to slot home.Florent Malouda shot at keeper Jason Brown before Blackburn saw Christopher Samba go close with a header.As Chelsea dropped deeper Michel Salgado burst down the right and Diouf out-jumped Paulo Ferreira to nod in.With Manchester United regaining top spot after beating Liverpool, it was crucial for the London side to keep breathing down the necks of their rivals and a single point on Sunday's travels means they remain third, four points behind the leaders with a game in hand.The Blues have now picked up only seven points out of a possible 15 as their hunt for silverware wobbled once again.Ancelotti retains league title hopesIt had all begun so brightly for Carlo Ancelotti's men with their opener inside six minutes and the manager would have been delighted, having remarked in the build-up that a possible FA Cup and League double was "in their own hands".Bouncing back from their midweek Champions League demise against Inter Milan would have been their top priority and there was no surprise in seeing the red-hot Drogba on the scoresheet.The goal was all down to the trickery of Anelka, who produced a jinking run on the right to carve open the Blackburn defence.His clever pull-back teed up Drogba and the Ivory Coast striker coolly slotted in with his left foot for his 22nd league goal of the season.Any confidence the hosts may have had on the back of their Carling Cup penalty shoot-out win over Chelsea three months ago seemed to immediately drain away and Drogba and Malouda wasted two chances to extend the lead.Sam Allardyce's team have lost at home only twice in the league this season and they at last showed some spirit as Morten Gamst Pedersen twice blazed over from outside the box.Despite missing a number of players through injury, which saw keeper Brown in for Paul Robinson, Blackburn were starting to rattle their London guests with a number of crunching tackles.There were none more committed that Phil Jones, the 18-year-old making his league debut, and his firm challenges on Drogba and Frank Lampard in the middle of the park on the half-hour significantly increased the noise levels inside Ewood Park.Just before the break Malouda was denied a goal by Brown and the chance was a result of Drogba showing that he is not just about goals.The tireless striker, hoping to make up for his sending off against Inter Milan, intercepted a Blackburn breakaway with a sliding tackle and set up Malouda, who strolled through the defence but shot straight at the keeper.Back came the hosts and they came close to an equaliser soon after the interval as Samba nodded on a long throw and would have found the net had it not been for the well-positioned substitute Yuri Zhirkov, who cleared the danger from the line.Allardyce desperately needed a change in momentum and introduced striker Jason Roberts for Nikola Kalinic - a decision not popular with the local fans.But the howls of derision turned into cheers on 70 minutes as Diouf stunned the Londoners.Chelsea seemed increasingly intent on sitting back and they paid a heavy price as Salgado's curling cross from the right fell to the leaping Diouf, who powered in a header past Ross Turnbull.There was still time for Drogba to see a shot pushed around the post by Brown and Chelsea also had a number of late corners as they piled the pressure on the home defence, but Blackburn survived.With Allardyce's stubborn and hard-working team still to play United and Arsenal, Blackburn have a vital role to play in the final destination of the Premier League trophy.Source: BBC