A review of Sunday's action in the FA Cup quarter-finals.
First-half goals from Javier Hernandez and the returning Wayne Rooney, back in the starting XI amid the furore over his future in the wake of his omission against Real Madrid, seemed set to secure a comfortable victory at Old Trafford.
Former Liverpool boss Rafa Benitez was being tormented by United fans with chants of, 'you're being sacked in the morning' but the under-fire Chelsea interim boss earned some respite thanks to Eden Hazard and then Ramires' equaliser.
It seemed certain Juan Mata would complete a memorable comeback when he stepped inside Jonny Evans in the final minute.
But David De Gea, so often the target of criticism, stuck out a leg to keep Mata out and United in the competition.
The replay will not suit Sir Alex Ferguson, still less so Benitez given it could potentially force Chelsea into four games in a week or trigger the postponement of a Premier League fixture.
Manchester City will provide the opposition for the winners at Stamford Bridge in the semi-finals.
Neither side could break the deadlock and will face a replay at Ewood Park to determine which team will represent the npower Championship in the semi-finals.
The 2004 finalists Millwall created more chances to win the game throughout the 90 minutes and Rovers, who are yet to concede in this season's competition, will be pleased to have left London with another chance of securing a trip to Wembley.
Andy Keogh hit a post and Danny Shittu forced a great save out of Blackburn's Jake Kean whilst the visitors did not register a single shot on David Forde's goal, although Joshua King saw a header hit the post with 13 minutes remaining.
A semi-final clash against Wigan will be the reward for the winner of Wednesday night's replay.