The Spain international said his team would have felt "humiliated" if they had lost to Manuel Pellegrini's youngsters and feels his team are starting to improve
There were six teenagers and five full debutants in the City line-up, as Manuel Pellegrini stayed true to his pledge to rest key players ahead of this week's Champions League trip to Dynamo Kiev and next Sunday's League Cup final with Liverpool.
Striker David Faupala marked his maiden City appearance by cancelling out Diego Costa's first-half opener, but Chelsea's experience and class told after half-time.
Willian, Gary Cahill, Eden Hazard and substitute Bertrand Traore were all on target and Fabregas said the opposition team-sheet raised eyebrows in the Blues' dressing room.
"I must admit, yes [it was a surprise]," he told BBC Sport. "I don't know whether this is a positive or a negative… for us it was probably negative because it puts more pressure on us.
"If you lose against this type of team everyone would say you are humiliated."
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Fabregas was one of the players strongly criticised in some quarters as Chelsea's Premier League title defence fell apart during the first half of the season and boss Jose Mourinho paid with his job.
They have been rejuvenated under Hiddink and, with an FA Cup quarter-final tie at Everton to come and the Champions League last-16 tie in the balance, the Spain international is confident of ending the season with silverware.
"You can see straight away we are playing better and better," Fabregas added.
"The confidence grows when you are winning – it happens in football as it happens in any part of life.
"We have big games coming up and the Champions League is a big challenge, we need to be ready for anything."