The Dismal Performance of "Stars"

Seeing C. Ronaldo on the pitch last night made me wonder why he was so worse than he was in Real Madrid. In fact, his performance was the rule rather than the exception: Many other football stars have been invisible in South Africa, so after a bit of brainstorming, I came with the following hypotheses:

1. Just don't care: Players like Ronaldo make millions of euros each year; an injury suffered at the World Cup would cost them a lot. Besides, they have already proven themselves, so they have no need (unlike Germany's Muller) to increase their value by performing exceptionally at the World Cup. This is incentive theory in action.
2. Externalities: It could also be that national teams are less suited to a star than top club teams. There could be quite a few reasons for this: For example, if you are spending 100 millions euros in Ronaldo, you want to make sure he will be paired with player(s) suited to his style in the attack line. National teams have no such luxuries; while they choose the best of the nation, they have a much narrower pool than club teams, especially club teams like Money U. Barca and Real that have no real budget constraints.Or it could be that star players perform better when they are surrounded by good players who can, for example, pass the ball to them.

A soft test of the first hypothesis would be to compare the performance of stars at the World Cup with their first World Cup performance when they were budding stars. Or for each World Cup, you could compare the performance of established stars with youngsters who actually turn into starts in a few years' time.

To test the second explanation is more direct, at least for me: I would expect to find a positive relationship (after controlling for other stuff of course) between a star player's World Cup performance and the difference of rankings between the national team and club.

Anyway, which explanation, do you think, is more prevalent? To me, there is some of each going on here: To give two examples from my favorite World Cup team (so far), for Mesut Ozil, the externality effect could be more prevalent, whereas for Thomas Muller, it could be all about proving himself. BTW, you could easily test both explanations together in a single regression, of course.

Or, do you have an alternative explantion?