A 79th minute penalty from Frank Lampard won a pulsating clash between Chelsea and Manchester United at Stamford Bridge.
In a game of two halves, United took the lead in the first period through a 20 yard strike from Wayne Rooney.
However, second half goals from David Luiz and Frank Lampard from the spot secured a crucial win for Carlo Ancelotti’s side in a match the manager said would define their season beforehand.
Nemanja Vidic saw red late on for two bookable offences, although Luiz was lucky to avoid a second yellow when the scores were level, taking Rooney down off the ball and out of the referee's sight.
It was a match that lived up to the hype from the off, with Fernando Torres putting the ball in the net early for the Blues, only to see his strike disallowed for an earlier foul from the original corner.
After fairly even exchanges, Rooney drove home to give the Red Devils the lead on 30 minutes. The England international received the ball outside the box and was allowed time to turn and shoot, firing into the bottom right hand corner past the despairing Petr Cech.
Chelsea chased the leveler, and Branislav Ivanovich will still be wondering how he failed to level from close range as half-time approached. Frank Lampard's low free kick was parried by Edwin Van der Sar, and the Dutch international reacted brilliantly to get hands up and stop the Serb bundling the ball into the net.
The home side grew even stronger in the second period, and started applying pressure to United in their search for an equaliser. Luiz delivered with a 59th minute volley, with the Red Devils failing to clear their lines and the Brazilian finding the bottom left corner.
Didier Drogba was introduced, but it was fellow substitute Yuri Zhirkov who made the difference when arriving off the bench.
It was the Russian who was adjudged to have been fouled by Chris Smalling, and Lampard who smashed home the decisive penalty on 80 minutes.
Zhirkov then struck the post with a fierce shot a couple of minutes later, Vidic deflecting the ball onto the post and saving a third goal.
The Serbian skipper was to end the match early though, pulling down Ramires as time ran down to receive his marching orders.
Victory keeps Chelsea's very feint title hopes alive, but it's Arsenal who benefit most as the Barclays Premier League title race has been blown wide open.