As Robin van Persie shaped to shoot through a crowd of players at the Stretford End four minutes into stoppage time, Chelsea's title rivals might have been starting a sharp intake of breath.
It is too early in the season to suggest the outcome of the Premier League hinged on Van Persie taking a win away from Chelsea and earning Manchester United a point - but not too early to say manager Jose Mourinho was only seconds away from a victory of huge significance.
Had Chelsea survived that frantic finale and secured the lead Didier Drogba's goal had given them, they would have been six points clear of Southampton and, more importantly, eight points clear of champions Manchester City.
Van Persie, to the great relief of Manchester City ironically enough, finally breached the barrier erected by Chelsea's magnificent young goalkeeper Thibaut Courtois and Mourinho's men remained in sight of those hoping to catch the Premier League's outstanding team.
Mourinho turned on his heel in frustration but gathered his composure enough to ascend the stairs behind the technical area and embrace his old mentor and now United manager Louis van Gaal at the final whistle. This was, after all, still an important Chelsea display in the title context.
So what pieces can be picked from an enthralling Old Trafford encounter?
Chelsea still the team to beat
Van Gaal made a strong case that United deserved their point - but there was an ominous air of authority about Chelsea at Old Trafford until the chaotic conclusion that saw Branislav Ivanovic sent off for a second yellow card and Van Persie score.
When Chelsea drew 0-0 at Old Trafford in a dull stalemate last season, they lacked a potent striker and struggled to impose themselves in David Moyes's first home game as United manager.
|Peter Schmeichel: "Manchester United and Chelsea have excellent young goalkeepers in David de Gea and Thibaut Courtois but, in front of them, things are very different. Courtois plays behind an incredibly well-organised defence. In contrast, United's back four is full of uncertainty and insecurity, something that was particularly evident at set-pieces at Old Trafford."|
|Read more: Man Utd disorganised in defence|
Mourinho walked away from Old Trafford that August night happy with a point, a sign that Chelsea were one of his works-in-progress.
What a contrast here as the Portuguese heaped praise on his players and illustrated that the aims this time were different. It was clear he was disappointed to leave with the same share of the points.
"I'm so happy with my players," he said. "I got the same result here last season but what we did today in comparison showed the evolution in this group. We are not happy with this point and this is only possible when you think we are so good and you are not happy with the result."
And evolve Chelsea have, both buying in class and going back for the future by bringing back some old faces. In Premier League terms they look close to completion.
Goalkeeper Petr Cech has been one of the Premier League's most enduring figures but the performance of Courtois in the Old Trafford hothouse simply confirmed the time for succession was right.
Matured by his seasons on loan at Atletico Madrid, the 22-year-old Belgian has returned to the Blues in outstanding shape. He was authority personified against United, commanding his area, handling impeccably and saving superbly from Van Persie when called on.
He even threatened to have the final word with a wonderful save from Marouane Fellaini - only for Van Persie to hammer in the rebound.
Since last year, Nemanja Matic has returned in a £21m deal from Benfica and Didier Drogba is also back in the fold after leaving Galatasaray.
Drogba headed Chelsea's goal while Matic, whose frame seems to cover almost the width of the centre circle at times, is the glue that holds Chelsea together.
To emphasise the increased strength this season, Mourinho only turned to Drogba because £32m leading scorer Diego Costa continues to be troubled by hamstring problems and another summer signing Loic Remy was also injured.
Cesc Fabregas was not at his most influential on Sunday but his class is clear. He is part of a Blues team in which most struggle to find any serious weaknesses.
Chelsea have not been able to match the flawless 27 points from nine games under Mourinho when he won his second title in 2005-06 but, with 23 points, they are three ahead of the tally they had accumulated at this stage in his first triumphant campaign at Stamford Bridge in 2004-05.
Manchester City look to be the only team capable of catching them - but they do not have Chelsea's consistency so far.
|Chelsea after nine Premier League games in seasons with Mourinho|
|Season||Wins||Points||Final finishing position|
|* - Mourinho left the club on 20 September 2007|
The return of 'Fergie time'
It was just like old times at Old Trafford as United piled players into the penalty area at the Stretford End in the melee that led to Van Persie's equaliser.
A sign of the paucity, and perhaps ill-luck, of the Moyes era was that this was the first time United had scored in injury time in the Premier League to turn a defeat into a draw - or a draw into a win - since Van Persie scored the winner in the 3-2 derby victory at Manchester City on 9 December 2012.
Van Gaal can rightly point to this as another of the improvements he is seeking - and it will also delight United fans who appeared to have given up on those late charges throughout the misery of last season.
And despite Chelsea looking in control for the most part once they went ahead, it is to United's credit that they never gave up pushing for that equaliser.
Van Gaal said: "Chelsea is the best club in Europe at killing the game but my boys kept going, created one or two chances and scored a goal. They found what they needed at the end and it was very, very deserved."
Marouane Fellaini's Manchester United career looked to have been finished by a disastrous first season, when he was effectively the symbol on the field of the failed appointment of Moyes - a £27.5m misfit captured in what seemed a late act of transfer panic.
And yet, in 169 Premier League minutes under Van Gaal, the giant Belgian has suddenly shown signs of life and given himself some hope of surviving at Old Trafford.
Fellaini came on as substitute to score a brilliant goal at West Bromwich Albion and demonstrated that he is best used as an attacking threat by forcing the save from Courtois that led to Van Persie's goal.
There is a horrible image from last season of Fellaini surging out of defence but controlling the ball so badly, on several occasions in the same move, that he ended up chasing his own error into touch. It betrayed his total lack of confidence. Here, he looked like he finally felt at home.
He can be a threat in a more attacking role, not the one he favours but the one he is best at. This is an over-populated area at Old Trafford but at least he has, this week, looked like he can make a contribution.
|David de Gea: 7||Thibaut Courtois: 8|
|Rafael: 7||Filipe Luis: 7|
|Chris Smalling: 6||John Terry: 6|
|Marcos Rojo: 5||Gary Cahill: 7|
|Luke Shaw: 6||Branislav Ivanovic: 6|
|Adnan Januzaj: 6||Cesc Fabregas: 5|
|Juan Mata: 5||Eden Hazard: 8|
|Angel Di Maria: 6||Willian: 6|
|Daley Blind: 5||Oscar: 6|
|Robin van Persie: 6||Didier Drogba: 7|
|James Wilson (sub): 5||John Mikel Obi (sub): 5|
|Marouane Fellaini 8At last, signs of the player seen at Everton, not the lost soul of last season. Battled for everything and helped set up the equaliser||Nemanja Matic 9A magnificent display from the Serb. A formidable presence, towering in all senses of the word. Ruled midfield with such authority|
Manchester United may have done neighbours City a favour on Sunday - but will they damage them in the season's first derby at Etihad Stadium next weekend?
Wayne Rooney will be back from suspension and Van Gaal will hope to build on the good signs he saw on Sunday.
City will be desperate to win, not simply for local pride but because you will not find many takers for QPR getting anything from their visit to Stamford Bridge. Manuel Pellegrini's side will want to stay on Chelsea's heels.