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.
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.
For Liverpool counterpart Benitez, he watched his side fade badly as they lost further ground in the battle for fourth spot and a place in next season's Champions League.
Ferguson and Benitez made a single change each to their teams, with Park replacing Dimitar Berbatov for United and Maxi Rodriguez coming in for Ryan Babel in the Liverpool line-up.
United's boss insisted they had learned the lessons of being terrorised by Torres last season - but apparently not well enough as the Spain striker quickly emphasised his class.
Gerrard released Kuyt on the right, leaving Torres to escape from Vidic and Ferdinand to plant a firm header beyond the reach of Van der Sar.
United were level seven minutes later in contentious circumstances, following referee Webb's decision to award a penalty after Valencia tangled with Mascherano. It was a foul, but Liverpool felt the infringement started outside the area and chaotic scenes ensued.
As Liverpool boss Benitez raged on the touchline, Torres kicked away the penalty spot markings in fury as Rooney complained about the delay.
Liverpool keeper Reina blocked Rooney's spot-kick, but the rebound fell kindly for the England striker to slot home into an empty net.
Ferguson and Benitez were then involved in an angry exchange almost nose-to-nose in the technical area, with fourth official Marriner in between the pair in an attempt to keep the peace.
Valencia was United's main source of danger as he tormented Emiliano Insua down the right flank, and his cross almost created a second for Park as he headed just wide with Reina scrambling across his goal.
Torres, in particular, appeared aggrieved by what Liverpool saw as a grave injustice and he took his frustration out on Park to earn an overdue yellow card, his fifth in seven games.
Reina was tested twice by Nani's shot and a Rooney free-kick from the edge of the area before the interval, but the game had settled after an explosive opening.
The sparring continued in the early stages after half-time, but United managed to pierce the massed ranks of Liverpool's defence to take the lead after an hour. Fletcher was the creator with a perfect cross from the right flank, and Park bravely hurled himself in front of Johnson to head beyond Reina.
Rooney had been hugely industrious in his efforts to ensure United's victory, and he was almost on the scoresheet again with four minutes left, but he pulled a low shot just wide.
Liverpool had barely troubled United in the second half, but with only a minute remaining of normal time they conspired to waste a wonderful chance to snatch a point.
Gerrard, an anonymous figure until then, set up Torres with a cross. He mis-hit his shot, but it lofted invitingly into the path of Benayoun, who headed straight at Van der Sar from only six yards.
United were then able to play out five minutes of stoppage time - and the celebrations from players and fans at the final whistle illustrated just how vital this victory was to the champions.