Robin van Persie's equaliser deep into injury time gave Manchester United a point and kept Chelsea within range of their Premier League title rivals after a dramatic Old Trafford finale.
Didier Drogba's header looked to have extended Chelsea's lead at the top of the table to six points until a thunderous conclusion in Manchester.
Chelsea's Branislav Ivanovic was sent off after a second yellow card for a foul on Angel Di Maria one minute before the end of the game.
Di Maria's free-kick straight after this saw Chelsea goalkeeper Thibaut Courtois save brilliantly from Marouane Fellaini but Van Persie was on hand to thrash home the rebound and spark wild celebrations around Old Trafford.
Blues manager Jose Mourinho turned away in disgust as Van Persie scored, frustrated that the victory his side deserved for controlling long periods had slipped away.
The Portuguese's side remain four points clear of second-placed Southampton - and, perhaps more significantly, six points ahead of last season's champions Manchester City.
For United manager Louis van Gaal, there will be pleasure in showing the resilience and fighting spirit of old to earn a point - but also the reality that Chelsea showed him how much ground they still have to make up, despite that £150m spending spree on new players this summer.
Premier League weekend results
Man Utd 1 - 1 Chelsea
Burnley 1 - 3 Everton
Tottenham 1 - 2 Newcastle
West Ham 2 - 1 Man City
Liverpool 0 - 0 Hull
Southampton 1 - 0 Stoke
Sunderland 0 - 2 Arsenal
West Brom 2 - 2 Crystal Palace
Swansea 2 - 0 Leicester