Manchester United are back on top of the Premier League for the first time in 770 days as the landscape suddenly shifts and Manchester City go from looking invincible to vulnerable.
United's 3-0 win over Sunderland saw them overhaul neighbours City -who lost 4-1 at Tottenham - to occupy a position they have not held since the first match of David Moyes' abysmal reign as manager, when they won 4-1 at Swansea on 17 August 2013.
And while this was a symbolic result rather than a statement of title intent, there were events elsewhere that made it a day of Premier League significance.
Are Man Utd genuine title contenders?
Manager Louis van Gaal can study the table with quiet satisfaction - but he will know this is merely an opening salvo and much work needs to be done.
Even so, with City losing and Chelsea's defensive frailties without captain John Terry exposed as they were held to a draw at struggling Newcastle, Van Gaal might be tempted to burst into song once more at Saturday's developments.
Chelsea manager Jose Mourinho - who has never won a league game on Tyneside - was ultimately grateful for a point after his side came from two goals down late on to earn a draw.
It was, however, an unconvincing performance from the reigning champions, who are 15th, and one that suggested plenty of problems still need to be solved before they return to the authority of last season.
United's title credentials may become a lot clearer after their next three games, which take them to Arsenal, followed by a trip to Everton that often ends in disappointment then the Manchester derby at Old Trafford on Sunday, 25 October.
What is certain is that the cards have fallen in United's favour in recent weeks and suddenly the future looks a lot brighter.
The failure of goalkeeper David de Gea's proposed move to Real Madrid followed by the 24-year-old's decision to sign a new four-year deal not only ended uncertainty and lifted the mood around Old Trafford, it meant United could restore a goalkeeper who is deservedly ranked among the best in the world as their last line of defence.
De Gea's mere presence increases United's chances of success - while the £36m move for 19-year-old Monaco striker Antony Martial on transfer deadline day is starting to look like a masterstroke.
The world's most expensive teenager has not only scored three goals in three Premier League games, he has demonstrated a natural eye for a finish and the sort of raw pace that will unsettle any defence.
Martial's impact looks certain to provide more space and opportunities for Wayne Rooney as an attacking foil - while Van Gaal will also be pleasedMemphis Depay got on the scoresheet against Sunderland.
So it is too early to say if United can challenge for the title - and realistically the odds are still against with visits to all their serious rivals to come - but there has never been any bad news in being top of the table.