Interim Chelsea manager Guus Hiddink claims Manuel Pellegrini's decision to name a young Manchester City team did not help his side in their 5-1 FA Cup fifth round win at Stamford Bridge.
Diego Costa put Chelsea ahead but City struck back through debutant striker David Faupala, before Willian, Gary Cahill, Eden Hazard and substitute Bertrand Traore sealed Chelsea's place in the quarter-finals.
Facing a side including six teenagers and five full debutants, Hiddink labelled his players' ruthlessness as "key".
"Manchester City made changes but that doesn't make it easy because the youngsters that came in were dangerous," Hiddink told BBC Sport.
"It was key that we started well in the second half, got an early second and third goal."
Chelsea will travel to Everton in the quarter-finals in a repeat of the 2009 final, in which Hiddink led the Blues to a 2-1 victory during his previous spell in charge of the club.
"That was a long time ago," said Hiddink, who is unbeaten in six FA Cup ties as Chelsea's coach.
"I think they will be gunning for revenge. The past is the past.
"Everton at their home is difficult, of course, but we hope to keep this flow we are in and maintain it to the next round."