It may sound crazy to suggest that the reigning world and European champions could falter, but clear precedents have been set for this in the past.
France turned up in South Korea and Japan in 2002 with the aim of defending their trophy, but they ended up losing to Senegal and Denmark, finishing at the bottom of the group with a single point from a draw with Uruguay. Equally, in 2010, the Italians, who won the previous tournament, couldn't get a win in a group that featured famous football powerhouses Paraguay, Slovakia and New Zealand.
Spain are obviously a strong squad and among the favourites, but they often start tournaments slowly (remember the opening loss to Switzerland in 2010?).
There are also concerns that some of the Golden Generation are reaching the autumn years of their careers, but the biggest threat might be the death of "tiki taka."
In Europe this season, we have seen teams who play a beautiful passing game (like Barcelona and Bayern Munich) overshadowed by those high-energy, counter-attacking sides (like Chelsea and both Madrid teams).
The tactical balance might be shifting toward "reactive" counter-attacking, a fact the Spanish might discover in a group that features a high-pressure Chile side.