Manchester United came from behind to beat Liverpool at Old Trafford to return to the Premier League summit.
Fernando Torres was United's tormentor again as he rose to head in Dirk Kuyt's cross after only five minutes to revive memories of Liverpool's crushing 4-1 victory here last season - but United were to exact revenge on their arch-rivals.
Liverpool were furious when United were handed the opportunity to draw level swiftly as referee Howard Webb awarded a penalty as the outstanding Antonio Valencia was hauled back by Javier Mascherano as the pair raced into the area.
Wayne Rooney was unsettled by Liverpool's lengthy and vociferous protests, but when his penalty was saved by keeper Pepe Reina he was first to react and turn in the rebound. Manchester United assistant coach Mike Phelan
Man Utd perseverance pleases Phelan
United then held sway and snatched a deserved winner on the hour when Darren Fletcher's cross deep into the heart of the Liverpool penalty area was headed in by Ji-Sung Park.
Liverpool boss Rafael Benitez, who confronted fourth official Andre Marriner and United boss Sir Alex Ferguson after Rooney's equaliser, was infuriated by the penalty award - and was also animated throughout by what he clearly regarded as a succession of contentious decisions that he believed went in the home side's favour.
Goalscorer Torres led Liverpool's other complaints against officialdom, and he became increasingly frustrated at virtually having to battle single-handedly against Rio Ferdinand and Nemanja Vidic, who ended an unwanted record of three dismissals in his last three games against the Merseysiders.
Liverpool captain Steven Gerrard was desperately disappointing, although he created a late opportunity which Torres missed. Yossi Benayoun should have done better than head the loose ball tamely at Edwin van der Sar.
Ferguson will have regarded this as one of the most difficult tests of United's title run-in, and his succession of clenched-fist salutes at the final whistle demonstrated his delight.
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.
