Manchester United threw away a two-goal advantage after second half strikes from Eden Hazard and Ramires secured Chelsea a 2-2 draw at Old Trafford, ensuring the Blues' defence of the FA Cup remains intact, taking the quarter-final clash to a replay.
It was a stunning fightback from the visitors, who looked dead and buried after just 11 minutes, as United took an early lead, courtesy of Javier Hernandez and Wayne Rooney.
The Mexican forward, recalled in place of Robin van Persie - had to settle for a place on the bench - headed home Michael Carrick's pass, before Rooney made it 2-0 when his curling free-kick bypassed everybody in the Chelsea box, nestling into the far corner of Petr Cech's goal.
Rafa Benitez introduced Hazard after the break, and it wasn't long before the Belgian had given the away side a huge lift, scoring a fine curled effort of his own just before the hour mark.
Brazilian midfielder, Ramires, then completed the dramatic comeback nine minutes later, finishing off a slick Chelsea counter-attack.
Manchester United goalkeeper David De Gea deserved credit from preventing a total turnarond, after he denied Juan Mata in the closing stages.
Rooney could have added to his goal after returning to Sir Alex Ferguson's starting line-up, having been dropped for the midweek Champions League clash against Real Madrid, but was denied by Cech, who did well to divert David Luiz's attempted clearance for the Blues.
Chelsea are back in Europa League action on Thursday when they host Steaua Bucharest in the second leg of their last-16 clash, so a replay with Manchester United is not possible this week, meaning there is not yet a fixed date for the second installment of the FA Cup sixth round clash at Stamford Bridge.
Manchester United: De Gea; Rafael, Ferdinand, Evans, Evra, Carrick, Cleverley, Kagawa (Welbeck 76'), Rooney, Nani (Valencia 45'), Hernandez (Van Persie 62').
Subs not used: Amos, Vidic, Anderson, Young.
Chelsea: Cech; Azpilicueta, Luiz, Cahill, Cole, Ramires, Lampard (Mikel 52'), Moses (Hazard 52'), Mata, Oscar, Ba (Torres 77').
Subs not used: Turnbull, Terry, Ivanovic, Bertrand.
Venue: Old Trafford
Referee: Howard Webb