Robin van Persie’s last-gasp goal rescued a point for Manchester United as Louis van Gaal and Chelsea boss Jose Mourinho shared a 1-1 draw.
The Portuguese looked to be heading for a famous victory against his one-time mentor at Barcelona after Didier Drogba’s second-half strike had given Chelsea the lead.
But deep into injury time – and after Branislav Ivanovic had been sent off for a second bookable offence – Van Persie pounced on a half-cleared free-kick to smash home an equaliser.
The point means that Chelsea’s lead at the Premier League summit is now four points over Southampton, while they are six points better off than Manchester City following the defending champions’ 2-1 defeat at West Ham on Saturday.
United, meanwhile, were held again after their lacklustre 2-2 draw against West Brom on Monday.
Marouane Fellaini was rewarded for his goalscoring appearance in that game with a start in midfield at the expense of Ander Herrera, while Chris Smalling replaced the injured Phil Jones at centre-back.
Diego Costa and Loic Remy missed out for Chelsea due to a virus and a groin problem respectively, meaning Drogba played as their attacking spearhead.