Manager Frank Lampard said Chelsea will go through “periods of pain” after watching them lose 3-1 to Manchester City at Stamford Bridge.
Chelsea have taken only four points from their past six Premier League games.
Sunday’s loss left them in eighth place, having played at least one match more than six of the teams above them.
“Any rebuild takes pain – pain behind the scenes and on the pitch,” Lampard said.
“This is a difficult period and I understand the reasons why. When you look around the team there is a lot of youth, a lot of new players who are trying to come in and settle.”
Chelsea spent more than £200m in the last transfer window, signing Timo Werner, Kai Havertz and Edouard Mendy.
They could have gone top of the table with victory over Everton on 12 December, but now find themselves seven points adrift of leaders Liverpool.
“I was real after we beat Leeds (on 5 December) saying that we’re not title contenders, and I’m real now saying it takes time,” said Lampard.
“I’ll always feel the heat. I felt the heat when we were on our good run, because I know that round the corner can be a negative.”
Ilkay Gundogan, Phil Foden and Kevin de Bruyne scored in the space of 16 first-half minutes to put the game beyond Chelsea, for whom Callum Hudson-Odoi grabbed a stoppage-time consolation.
Lampard refused to comment on his future after suffering a first defeat at home since the 2-0 loss to reigning champions Liverpool in September.
“I’m not going to speak for people above me or the board – it’s not for me to do that,” he said.
“I can’t think about what people say because I can’t be distracted.”
‘It could have been five or six’
Former Chelsea goalkeeper Rob Green told BBC Radio 5 Live that City “could have been five or six up at half-time”.
“Man City blew Chelsea away,” said the 40-year-old ex-England international. “As a Chelsea player, you’d think you’re going to have to ride the storm here, but they didn’t.
“The first five minutes and the last 30 seconds – they’re the only times Chelsea looked like doing anything. [Hudson-Odoi’s goal] was the one time in the whole game that Man City were stretched.
“They were so tight and compact defensively for the whole game.”
‘We’re here fighting’ – De Bruyne
Victory lifted City to within five points of Liverpool with a game in hand.
The visitors had to survive a spell of early Chelsea pressure but soon overpowered their hosts to race into a comfortable half-time lead.
“After five or 10 minutes we found our rhythm,” De Bruyne told Sky Sports.
“We took our chances at the right time. Leading 3-0 at half-time meant we could play more realistic in the second half.”
Having lost to Leicester and Tottenham and drawn with Liverpool and Manchester United, this was City’s first win of the campaign against one of last season’s Premier League top six.
“It’s important that we win one of these big games,” said De Bruyne. “The years we were champions, we were winning them. It’s a bit different this year because everyone is losing points.
“We had a bad start but we are coming back a bit, so it’s a good thing we’re here fighting. That’s all we can do now.”