pellegrini is feeling the heat after man city 's 2-1 defeat to crystal palace .
the result left man city nine points behind chelsea in premier league .
the last four managers to win title have left their posts soon after .
jose mourinho 's first spell at chelsea abruptly ended in 2007 .
carlo ancelotti suffered similar fate year after title success .
roberto mancini was shown door by city 12 months after first league title .
sir alex ferguson retired after winning a 13th premier league at united .
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