City were hosting Premier League leaders Liverpool at the Etihad.
Defeat would send Liverpool 10 points clear while victory would leave City just four points behind - a huge swing one way or the other - and a game City had to win.
The decisive moment came around 17 minutes in as Sadio Mane's shot beat Ederson and hit the post - John Stones' attempted clearance hit Ederson and the ball was heading into the back of the net when Stones made one last attempt to prevent a certain goal...
Stones lunged and hooked the ball away - it was desperately close - and City fans waited to see if the goal-line technology would indicate a goal had been awarded.
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But the whole ball hadn't crossed the line - it needed 1.12cm more to have done so - and the score remained 0-0.
City then went on to win 2-1 with a goal from Sergio Aguero on 40 minutes and late winner from Leroy Sane.
Fine margins indeed.
Wednesday’s #City30 topic: best corner.
Which corner do you remember best and why? Was it one that resulted in a crucial winning goal or maybe just ended with a stunning volley. Whatever the moment, let us know.
Share your nominations on Twitter @ManCity.
Don't forget the hashtag #City30!