Germany winger Sane twisted his ankle when he was caught by Joe Bennett's shin-high challenge in the first half of City's 2-0 victory at the Cardiff City Stadium.

Bennett was given a second yellow card in injury time for a poor challenge on 18-year-old Brahim Diaz, and Guardiola looked unhappy as he spoke to referee Lee Mason at full-time.

"He [Sane] will be out for a while," Guardiola told a news conference. "Minimum two, three weeks or a month, we will see tomorrow exactly.

"I said many times, the only thing they [referees] have to do is protect the players. Not the Manchester City players, all players.

"It [a bad challenge] happened once and it happened again at the end with Brahim. So for football in general, for the players, who are the artists, we have to take care of them."

Bennett's horror tackle also drew a reaction on social media from the German Football Federation.

Looking ahead to the World Cup in Russia, the DFB tweeted: "Hey CardiffCityFC. Just letting you know, we have a really important tournament in the summer. Please don't hurt our players. Thanks."

Kevin De Bruyne put City ahead in the eighth minute with a clever free kick under the Cardiff wall before Raheem Sterling headed in a second after Bernardo Silva had seen a goal ruled out.

Guardiola said he had no problems with Cardiff's tough-tackling style and said he was proud of how his players coped with it.

"That's why football is nice, everybody can play," he said. "So Neil and his teams play in this way, like they did really well, marking to man, so aggressive, long balls.

"Again, I have no words to describe my pride about my players and my team. We know how many, many games we play, players with problems, a few players with a lot of minutes.

"Again, they are ready to play every three days, I feel something special about that. Playing FA Cup away, against a Championship team in the top of league, like Cardiff, it was so complicated, we reacted again like a mature team.

"So proud, congratulations, in the draw hopefully we can have a team at home -- that is my wish."

Cardiff boss Warnock said he was disappointed with Bennett for his second booking, which earned him a ban for the game at Leeds United on Sunday.

"We're in England, you are going to get challenges like that," he said. "We knew how they played. They caught us a few times and that is football, but obviously Leroy Sane is injured now and hopefully that is not too bad.

"It is unprofessional from Joe and then to commit one [another foul] in the 92nd minute. Maybe he does not want to go to Leeds on Saturday.

"He will be training morning, noon and night, I can tell you that."