Hardly anyone predicted that Sunderland would avoid defeat at Stamford Bridge this weekend, let alone wind up 3-0 victors, inflicting Chelsea's heaviest home defeat in over eight-and-a-half years, yet as soon as Nedum Onuoha put them in front with stunning composure, the visitors looked comfortable.
The Black Cats, who had won only one away match since last August, outplayed a side who had been comfortably the best in the country so far this season and it could had been even worse were it not for several smart Petr Cech saves in the first half and referee Chris Foy's refusal to send off Branislav Ivanovic.
So just what went so badly wrong for the champions yesterday? It was a loss that many considered to be on the cards after they went from winning their first five games in dominant fashion to taking three points in only four of their last seven, with no margin of success greater than two goals in that run.
However, the manner in which they were shown up in front of their own fans, looking toothless up front, lightweight in midfield and uncharacteristically fragile at the back, and failing to provide the expected second-half rally, was hugely surprising.
Was it just a case of the injury crisis getting too severe to cope with? Is their squad worryingly thin on quality and experience beneath the best XI? Was it really - as some have suggested - a reaction to Ray Wilkins' shock exit? Or was it a one-off freak result that will be recovered from and swiftly forgotten?
The fact that Carlo Ancelotti's Blues remain 1.87 title favourites despite having their lead cut down to just two points ahead of tough away games at Birmingham and Newcastle suggests most punters are leaning towards the latter.
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