Victor Moses and Diafra Sakho put West Ham United in a commanding 2-0 lead before Kevin De Bryne pulled one back for Manchester City just before the break.
But the Hammers' heroic defensive display in the second half thwarted wave after wave of City attacks to end Manuel Pellegrini's side's 11-match winning run in the Premier League.
So from a West Ham perspective, what did we learn from the game?
1) West Ham's wins at Arsenal and Liverpool were no fluke
Going into the game West Ham had already beaten Arsenal 2-0 at the Emirates Stadium on the opening day and Liverpool 3-0 in their last away game. In-between those matches, though, the Hammers lost 2-1 to Leicester City and 4-3 to newly-promoted Bournemouth.
That left some fans and pundits wondering whether those famous away wins were something of a fluke. But what Slaven Bilic's side proved on Saturday night is that they were anything but.
The East Londoners are so well set up to play away from home on the counter attack and boast pace, power and no mean skill to hurt even the best sides in the league.
One has to remember that City had not even conceded a goal this season, let alone a point, that's how big an achievement this was from the Hammers.
They will cause teams real problems on the road this season, and if their 2-0 win over Newcastle at the Boleyn Ground on Monday night was anything to go by their home form is back on track too.
2) The pundits were right West Ham fans, be careful what you wish for...
When West Ham dispensed of the services of Sam Allardyce in the summer, pundits and opposition fans were very outspoken on why the little old Hammers should be careful what they wish for.
Big Sam was a virtual guarantee to stay in the league, and that according to some pundits is the height of the club's ambition. Well, it seems they were all spot on, the Hammers should be careful what they wish for. With a new manager, some good signings and a new stadium they risk progressing as a club.
3) There is method to Chelsea's madness
When Victor Moses played a starring role on his debut in West Ham's 2-0 win over Newcastle, Chelsea – his parent club who had just lost 3-1 to Everton – were being castigated by their own fans on radio phone-ins and social media for letting him go.
One week later and the Blues' controversial use of the loan system – they had handed Moses a new deal before sending him out to the Hammers – has helped them back in the title race.
After Jose Mourinho's side beat Arsenal 2-0, Moses was crucial in Bilic's side's win at the Etihad. The thing is Chelsea know West Ham aren't going to rival them for league position over the course of the season.
So in letting Moses go to a competitive West Ham side, Mourinho knows he could well help them take points off their real rivals, such as City, Liverpool and Arsenal over the course of the campaign.
Agree with Chelsea's use of the loan system or not, it is working for West Ham, working for the reigning champions and the player is clearly enjoying himself.
4) Bilic was right to recall number one Adrian
Ahead of the game manager Bilic faced a real selection dilemma over which goalkeeper to plump for. Cult hero and club number one Adrian was sent off against Leicester City and has missed the three games since, a defeat to Bournemouth and back-to-back wins over Liverpool and Newcastle United.
In all three of those games stand-in 'keeper Darren Randolph – a free transfer from Birmingham City in the summer – performed very well and man argued he should keep his place until Adrian earned it back.
But Bilic showed the strength of character needed from a new manager in these situations making a clear statement that Adrian is his first choice and the Spaniard repaid his faith with a string of brilliant saves in the second half to deny City a way back and ensure another crucial three points.
5) West Ham finally have strength in depth
It says a lot about West Ham's strength in depth nowadays that they were missing two crucial players in Angelo Ogbonna and Chiekou Kouyate but had plenty of quality to step in seamlessly.
The likes of Andy Carroll didn't even make it on as a substitute and the Hammers look to finally have a squad not only capable of dealing with the injuries a typical Premier League season throws at you but also competing seriously in the cups.
Carroll, James Collins, Mauro Zarate and others could well get a run out in the cup, not a bad second string is it? Add the injured Alex Song and Enner Valencia to the mix when they return at the end of October/beginning of November, and the Hammers have quality options for almost every position.