The German winger ran virtually the full length of the field towards the end of the first half at the Cardiff City Stadium and looked to be through on goal before being cynically brought down by Joe Bennett.
The Cardiff man only received a yellow card, while Sane was taken off at half-time and is now expected to miss City’s game with West Brom on Wednesday.
It came after City were denied a clear goal when Bernardo Silva’s shot from the edge of the area that flew into the top corner was ruled out by the linesman who felt Sane was stood in an offside position - but replays seemed to suggest he was in line with the last defender.
Guardiola says he can accept an offside error – but believes referees aren’t offering enough protection to players.
“Sane will be out,” Guardiola said. “I don’t know how long for, I am not a doctor. Tomorrow we will see.
"They [officials] have to protect the players.
“Not my players. All players.
“They [refs] are there to protect the players. When there is fault, there is fault, and when it is dangerous, it is dangerous.
“I don’t understand the goal [Bernardo] that we didn’t get, but that is okay. We can accept that.
“But they have to protect the players. They have to do their job."
City’s win means we remain involved in all four major competitions.
We sit 12 points clear at the top of the Premier League, face a last-16 Champions League tie with Basel and are through to the Carabao Cup final to face Arsenal, which will be played next month.
And our win at Cardiff means we are now in the hat for Monday’s FA Cup fifth-round draw.
Guardiola says he is delighted with the efforts of his players but says our heavy schedule means winning an unprecedented quadruple is out of the question.
“I am delighted with everything,” he said.
“It is difficult to come to Championship sides who are topping the table. What they do they do really well.
“We play a lot of competitions and no rest and we are still fighting every game. So proud.
“No [we cannot win all four].
“The people ask me if we could be invincibles in the Premier League, I said no because we don’t have a large squad.
"A lot of players injured, Mendy six months, we played all the season without a left-back.
"But that is not a concern. Now we must recover for West Brom and Burnley and after we have to prepare for the Champions League [game at Basel].
"The important thing is the next ones.
"It is an illusion to think we can win all four. With this schedule it’s impossible."