It's a difficult one, tonight. You'd think that Spain would want to break some records, and that the 'second string' (who would probably give any side in the world a game anyway!) will be out to force their way into the first team. Although the opposition are hugely inferior, it's a chance to turn some heads. However, I agree with those who say that many of the Spanish squad will have some amount of respect for their opponents - I'm thinking of Casillas asking the referee to blow the whistle early in the Euro 2012 final, for example. Del Bosque certainly won't want to see his players milking it, but he won't expect a lack of effort, either.
Still, as much as Tahiti are the ultimate underdog, the fans won't want to see Spain refuse to attack. I think their players will feel awkward in terms of how to approach the match, but will probably thrash them without breaking sweat, and we won't see them performing any kind of big celebrations. In a strange way, it'll be a difficult one to prepare for mentally, but they'll win at a canter anyway so it won't matter.