I think LD's fitness level is also an important factor as he is probably one of the fittest if not the fittest player on the tour, so if a game does go into the rubber game, he is most likely able to maintain his level while his opponents will most likely tire, kinda like how Nadal usually can grind out a 5 setter in tennis....
No doubt that fitness is very crucial but with the new scoring system, the fitness is not as important as compare to 15-point system. Yes, I must say that LD is very fit... he looks very fresh after rubber games
