Frank Lampard said Chelsea will have to go through "periods of pain" to reach the standards set by Manchester City after Pep Guardiola's men outclassed the Blues in a 3-1 win at Stamford Bridge on Sunday.
City brushed off a series of coronavirus-related absences as goals from Ilkay Gundogan, Phil Foden and Kevin De Bruyne killed the game as a contest inside 35 minutes.
Victory lifts City to within four points of Liverpool and Manchester United at the top of the table, but with a game in hand on both to come.
Chelsea were expected to challenge for the title themselves after a £220 million ($300 million) spending spree in the transfer market, but a run of one win in six games has left them down in eighth, seven points off the pace having played a game more than the leaders.
Roman Abramovich has dismissed plenty of Chelsea managers in the past for similar spells of form and the pressure in mounting on Lampard to prove he can mould a talented squad of individuals into a team capable of competing for major honours.
"There are periods of pain we are going to go through. That was painful in the first half for the players," said Lampard, who publicly lambasted his side's effort in a 3-1 defeat to Arsenal last weekend.
"I'll be the first to look at myself today. When I look at this squad, I know there is uplift in this team but I know where we are at because I can see and I know the work it takes to be at the level Man City showed today.
"It's normal that as a squad we take little knocks along the way, now it is a test."
- City click into gear -
City had scored more than twice in a league game just once since their opening match of the season, but clicked into gear after taking 10 minutes to find their rhythm in an unfamiliar formation with De Bruyne the most advanced forward in between Foden and Raheem Sterling.
"We had a plan, we tried to play in a certain way and it worked, the players were fantastic in all departments," said Guardiola.
"We are a team that needs to play in a certain rhythm, we have to play a lot of passes. We won the Premier League that way (in the past).
"We missed a little bit this tempo (this season) and today we got it."
City were without Ederson, Kyle Walker, Ferran Torres and Gabriel Jesus due to a coronavirus outbreak that led to their clash at Everton on Monday being postponed.
Goalkeeper Zack Steffen was handed his Premier League debut, but was barely tested despite Lampard being able to start £150 million trio Christian Pulisic, Timo Werner and Hakim Ziyech together in attack for the first time.
Gundogan opened the floodgates on 18 minutes when he spun just outside the area and found the bottom corner.
Three minutes later Foden doubled City's lead with a fine near post finish from De Bruyne's cross.
"For 10 minutes we were good, then they started to play and we concede two poor goals," added Lampard. "I felt it knocked us and we didn't react."
Guardiola had only won once in five previous visits to Stamford Bridge as Barcelona and City boss, but his side were cruising by half-time.
All 10 Chelsea outfield players were caught ahead of the ball as De Bruyne released Sterling to run through on goal from inside his own half and after the England international hit the post, De Bruyne was first to react and slot home the rebound.
The scoreline could have been far more embarrassing for the hosts had City been more ruthless in the final hour as Foden, Gundogan, Rodrigo and De Bruyne all passed up big chances.
It is at the other end of the field City had sustained a title challenge while waiting for their forwards to find form in the past two months, but they just failed to record a ninth clean sheet in 11 games as Callum Hudson-Odoi slid in at the back post to claim a Chelsea consolation in stoppage time.