I agree. In that case, he can fight for every point because he has 1000 units of energy, everyone else has 500, and, well, there you have it...he can fight for

I agree. In that case, he can fight for every point because he has 1000 units of energy, everyone else has 500, and, well, there you have it...he can fight for the "pointless" points. But let me suggest that outclassing your opponents to such a degree in the real world is far less likely. In golf, for instance, Tiger Woods' early career exploited his far superior drive. As golfers altered their game / exercise approach, Tiger upped his game elsewhere to stay on top. Similarly, if Nadal faces an opponent with equal stamina, I think you'd see a far more strategic game. Or, to phrase it differently: the strategy he employs now (strategic use of endurance) will continue, but become more apparent as he is forced to make tradeoffs. That is, he currently 'picks his battles', but his superior reserves means he can pick each point. Against someone more equally classed, he'll continue to 'pick his battles', but more equal reserves mean we'd see different effects.