When this fixture was inexplicably postponed 27 hours before it was supposed to take place last December, the Premier League was bracing itself in the freezing temperatures for one of the crucial title showdowns of the season.
Fast forward two-and-a-half months and the match still carried great importance, but for only one of the two teams on show at Stamford Bridge.
Even the most optimistic of Chelsea fans must concede that being 12 points behind Manchester United with just ten rounds of games now left, even if they do have a game in hand, is too much to claw back. They cannot expect Arsenal to implode too.
So it is Arsenal who were the biggest winners just 48 hours after they were Carling Cup final losers.
Few could have predicted the turn of events when the two teams went in at the break. United had been superb for all but the first ten minutes of the match, with Paul Scholes pulling the strings as he always seems to do with consummate ease, Wayne Rooney bustling and bruising his way up top and Edwin van der Sar proving his timeless quality when called upon in goal.
Rooney's superbly struck opener was symptomatic of Chelsea's problems, as he turned unopposed from Nani's short pass to fire home his first Premier League goal from outside the area since scoring against Newcastle over three years ago.
Maybe it was left to John Terry to deliver a Scott Parker-style Churchillian address to his team-mates but, whatever was said in the changing room at the break, it worked as Chelsea were a different team in the second period.
Carlo Ancelotti sent his team back out playing with speed. Whereas before the break the Blues were ponderous both on the ball and off it, after it they were reinvigorated.
For those who had written Chelsea off as a spent force with no desire or team spirit, it was a 45 minutes which belied those accusations. It was a half of true character, grit and determination - but also of quality. It was no shock when the leveller came nine minutes after the break.
What was more of a surprise was the sight of defenders Branislav Ivanovic and David Luiz as the only two players in the box as Michael Essien lofted a ball towards goal. Ivanovic helped the ball on and Luiz fired home what will surely be the first of many in the Premier League.
United boss Sir Alex Ferguson was fuming at the performance of referee Martin Atkinson after the match, and there's little doubt that Luiz should not have been on the pitch at the end of the game. His deliberate blocking of Rooney was the most serious of his offences when already on a yellow - but some will point out that Rooney should not even have been playing following his own (unpunished) indiscretion against Wigan at the weekend.
When the winner came it was unfortunate for Chris Smalling, a signing which left many United fans scratching their heads 12 months ago but which now looks like a sound investment for the future. Yuri Zhirkov exposed his naivety in winning the penalty which would down United – after popping the ball between his legs - but for Smalling there will be greater days to come.
In the end, Nemanja Vidic received what seemed to be a certain red card for someone, as the tackles flew in - especially with referee Atkinson having handed out the most red cards in the Premier League so far this season. Vidic had walked the tightrope since being booked on the stroke of half-time, and his foul on Ramires in the 93rd minute was one too many.
Ancelotti may refuse to accept defeat in the quest to keep hold of his Premier League crown, but at least Chelsea are back in the Champions League qualifying places. With United travelling to Kenny Dalglish's Liverpool 24 hours after Arsenal entertain Sunderland on Saturday, it is odds-on that they will have to win at Anfield to keep their cushion over Arsene Wenger's men. That said, Arsenal's game in hand is away at their own arch-rivals, Tottenham, on Wednesday, April 20.
The crunch will surely come on Sunday, May 1 at Emirates Stadium when Manchester United visit the capital. For now, it's another side from across London who have had the greatest say in the title race.
• You can follow Dale Johnson on Twitter: @dalejohnsonESPN