With the score goalless, Stones produced a timely goal-line block after his attempted clearance had ricocheted back towards the City net off goalkeeper Ederson after Sadio Mane had struck the post.
Subsequent replays indicated that another couple of inches and a goal would have been awarded.
And Stones believed it was a key moment in what was a spellbinding match.
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"I tried to just take everything, he was coming back to his own goal and I spotted the opportunity and cleared it off the line,” said the England central defender.
“Fortunately, I reacted quite quickly and I'm just happy it didn't go over the line! Those sorts of things can change a game.
“You see it all the time where a keeper is shouting, and a defender comes and clears it.
“To be honest, I tried to take him, and the ball just had to react quickly!
“You realise what kind of situation you are in. In the first half we set a great tempo. We moved the ball quickly and created some great chances.
“We wanted to carry on that on in the second half and I think we did.”
The pulsating action on the pitch was also matched by a raucous atmosphere off it with the Etihad crowd providing superb backing from start to finish.
And Stones said he and colleagues fed from the crowd and vice-versa as he paid tribute to the City fans.
“I think everyone knew the magnitude of the game and wanted to get behind us,” said Stones.
“I think they feel the same passion as us. It was massive game to try and get closer to Liverpool.
“We’re still fighting and there are still so many games to play.
“We knew what we were playing for and I think we showed that in the way we played.”