Benitez’s days as interim Chelsea chief are numbered while Mancini is under pressure after 3½ years at City.
Benitez said: “People still talk about doing your job for three years and a work in progress but that’s not the case now.
“Having a boss like Alex Ferguson or Arsene Wenger for 20 years won’t happen any more. Not in England or any other big country.
“Things are going faster every year and you have to deliver.”