In all fairness to Rafa, I think he's done a very good job at Chelsea.
Lets be honest they were in a right state when he came in. Di Mateo (although they won the CL) is not a very good manager and was clueless as to what to do with all the players he had aquired. Roman for once went with the fans and decided to keep him on which was a major mistake.
Rafa has come in, and although it took him a while he has figured out a formation that works for them and has found a way with the rotation policy to get the best out of Mata, Hazard and Oscar. If he was kept on and made a couple of signings they'd challenge for the title and CL under him next season.
Also the way he has dealt with Terry and Lampard has been exceptional.
If Mancini was to go he wouldn't be top of the list but he's have to be on it.