The German winger damaged ankle ligaments after a heavy challenge from Cardiff’s Joe Bennett during Sunday’s 2-0 win over Cardiff in the FA Cup fourth round.
And as City prepare for a crucial Premier League game with West Brom on Wednesday evening, Guardiola says he expects Sane to spend an extended period on the sidelines.
“Leroy is injured," he said.
“It will be six weeks, seven weeks out.”
Cardiff boss Neil Warnock suggested Bennett’s tackle was indicative of the style of English football and intimated that Guardiola will have to get used to coming up against sides who adopt a physical approach.
Guardiola admitted Warnock, who began his management career in 1980, has more experience of the English game but says he disagrees with his assessment.
“He [Warnock] has more experience than me by far about English football,” Guardiola said.
“He knows it better than me. If he says that, what can I say.
“I have been here 18 months and I think English football is not like this.
“Again, Neil has more experience than me, a guy whose whole career was here in England. What can I say.
"He has spent all his career in England and that is why his opinions are his opinions."