Manchester City swept aside second-tier Cardiff City 2-0 with first-half goals from Kevin De Bruyne and Raheem Sterling on Sunday to reach the FA Cup fifth round in their quest to win an unprecedented four trophies this season.

The only sour note in an otherwise routine victory for the visitors was an ankle injury to winger Leroy Sane, which is expected to keep him out for a few weeks.

Pep Guardiola's side began without a recognised striker but took just eight minutes to go ahead when midfielder De Bruyne rolled a clever free kick under the wall as the defenders jumped to block the expected direction of his shot.

"The wall was close so I thought it would be easier to hit it under rather than over," said Belgian De Bruyne.

Bernardo Silva thought he had netted a spectacular second goal for the visitors with a long-range shot but Sane was flagged offside, a controversial decision that led to heated discussions between Guardiola and the fourth official.

City's dominance was never in doubt though and Silva turned provider for the second goal, perfectly directing a cross for the unmarked Sterling to head the ball into the net after 37 minutes for his 19th goal of the season in all competitions.

LATE DISMISSAL

Cardiff twice went close after the interval through Kenneth Zohore and Junior Hoilett but City always looked comfortable and Sterling and Silva spurned chances to extend the lead.

Danilo also drew an excellent save from home keeper Neil Etheridge before Championship side Cardiff's day got worse with the late dismissal of Joe Bennett for a second bookable offence.

His first clattering challenge on Sane led to the German's substitution at the interval.

"We knew how they played -- they caught us a few times and that is football," said De Bruyne.

Guardiola said Sane's injury would be assessed on Monday. "He will be out for a while, minimum two to three weeks or a month. We will see tomorrow exactly," he added.

The Spaniard again dismissed the notion that the quadruple was a feasible target for City this season even though they lead the Premier League by 12 points, face Arsenal in the League Cup final and are through to the Champions League last 16.

They lost their unbeaten league record in a 4-3 loss at Liverpool on Jan. 14 after Guardiola scotched suggestions they might be able to go through the domestic season undefeated.

Asked again on Sunday if City could claim the quadruuple he said: "No. They asked me if we would be invincible in the Premier League and I said no. I do not have enough players, I have players out injured. It is impossible."