The Premier League is highly regarded for its competitiveness, where anyone can genuinely beat anyone else on a given day - that kind of thing rarely happens in Spain and other European countries. There is no mystique or aura for defending English champions and it all means that when the naivety kicks in, as it has done in recent years, giants will always fall.
If it was naive to think that Chelsea were automatically favourites to win a second successive Premier League title ahead of the 2015/16 season - and it most certainly was - it's even more naive to think that now. Quite simply, Jose Mourinho's team have been left behind by their competitors and a terrible transfer window has now left them playing catch-up.
Essentially, Mourinho is playing the Football Manager game with real people. It's a foolproof plan and the easiest way of turning up money to improve the first team squad... Chelsea's transfer strategy is long term and it's such a strong blueprint that it's going to keep them at the pinnacle of English football for the years to come.
Players tipped for success have struggled and others have surprised, settling into life in the world's top league. Some teams have bought well and improved on last season's outing, but others have inexplicably struggled. Here is the ultimate collection of the Premier League's biggest over and under-achievers so far.