Chelsea captain John Terry was sent off on his first start since October as the Premier League leaders overcame League One Peterborough in the FA Cup.
The Blues made nine changes for the third-round tie and almost trailed when Asmir Begovic saved Lee Angol’s close-range header.
But Antonio Conte’s side had 20 shots by half time, with Pedro’s curled finish and a drilled Michy Batshuayi effort giving them a cushion, before Willian drove in from 18 yards after the break.
Terry saw red for bringing Angol down as the last man and Tom Nicholls prodded in from six yards for a buoyed Posh, only for Pedro to restore a three-goal advantage from the edge of the box.
Terry’s error will draw scrutiny but Chelsea were impressive in responding to defeat at Tottenham, their first in 11 matches in all competitions.
They exuded energy from the off, with players such as Nathaniel Chalobah and Ruben Loftus-Cheek impressing in midfield as Chelsea reached round four for the 19th season in a row.
Antonio Conte’s side will learn their opponents in Monday’s live draw on BBC Two and online from 19:00 GMT. The fourth round tie will take place on the weekend of 28 January, three days before they are scheduled to travel to second-place Liverpool in the Premier League.
Terry’s early bath
Conte felt Terry was hard done by, claiming the decision was “not right”.
But the central defender – who was making his 50th FA Cup start but only his eighth appearance in all competitions this season – clearly impeded the impressive Angol and he has now collected three of Chelsea’s last six red cards.
The ex-England captain, 36, instantly put his hands on his head and protested with referee Kevin Friend to no avail.
Before his early bath Terry had completed 100% of his 30 passes, though he only won 20% of his duels, less than defensive partners Gary Cahill (50%) and the fit-again Kurt Zouma (60%).
“John played a really good game,” added Conte. “For me, in this season he has shown me great ability.”
Ake will be available for future cup outings having not turned out in the competition for the Cherries and Chelsea’s central defensive options have hence been bolstered without spending a penny yet in the January transfer window.
But it was going forward against Peterborough where the seven-time FA Cup winners really shone. They took advantage by exploiting spaces left by the visitors’ positivity, none more so than when Batshuayi converted a smart Loftus-Cheek lay-off to clinically end a four versus two situation.
Batshuayi has played just 82 minutes of league football since his £33m summer move. Conte is keen not to let the 23-year-old leave on loan in January and his display underlined why as he proved a constant nuisance for the away defence.
The Belgian had claims for an early penalty and eight shots in all, drawing two good saves from Luke McGee and a fine last-ditch deflection from Gwion Edwards.
Chelsea have not lost in the third round since 1998. They managed 35 shots in all and it never looked like Peterborough would manage to frustrate them.
With Zouma back, Batshuayi firing, squad players in fine form and no added fixture in a replay to worry about, Terry’s red will be a mere blot on a good day for Conte.
Man of the match – Pedro
‘We showed we are a team’ – what the managers said
Chelsea manager Antonio Conte said: “I am pleased, when you change nine players it is never easy to play a good game and to be a team. Today we showed we were a team. I’m pleased for those who have played less as they have showed me good form.
On the return of Kurt Zouma, Conte added: “I am very happy. It is a first game after a really bad injury and he is fully recovered. He played good. We know he can improve a lot.”
Peterborough manager Grant McCann said: “I thought we were excellent. I thought we had two or three really good chances. I couldn’t believe Begovic saved from Angol.
“The biggest difference is how clinical they are. It is something we need to work on. I thought the boys were outstanding and in the second half we matched them.”
Unless the red card is overturned, Terry will miss Chelsea’s trip to Premier League champions Leicester next Saturday. Peterborough, ninth in League One, travel to Bury, who are in the bottom four.