Guardiola's runaway leaders fell to only a fourth Premier League defeat of the season as Bielsa's Whites left Manchester with all three points despite playing over half of the game with ten men.
Leeds captain Liam Cooper was shown a straight-red card for his challenge on City striker Gabriel Jesus in first-half stoppage time, four minutes after the Whites had gone ahead through a crisp strike from Stuart Dallas.
City eventually equalised through Ferran Torres in the 76th minute but Leeds countered to bag a late winner as an ice-cool Dallas slotted home his second goal of the game after being played in by Gjanni Alioski in the 91st minute.
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Guardiola's side had 29 shots at goal but Leeds had a golden chance to net again shortly before Dallas struck for the second time when Brazilian winger Raphinha raced clear one-on-one only to be thwarted by a sliding tackle by City 'keeper Ederson.
The City custodian denied 24-year-old Raphinha what would have been a seventh goal of the season as part of a stellar first campaign in English football that has also seen the £17m recruit from Rennes bag six assists.
Guardiola, though, was asked about Raphinha at his post-match press conference and admitted Leeds had a gem of a player on their hands who was continually improving under Bielsa's tutelage, akin to every player within the Whites squad.
"Of course he's a weapon, an exceptional player with good pace," said the City boss.
"Every player under Marcelo is getting better.
"He played a good game."
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Thank you Laura Collins