Well, there are much stranger things. For example what should we think about the big 3 who keep playing long matches and winning at their age? And that's after all of them had periods when it looked like they are done. Maybe they just work on it. To be honest, I really hope that tennis is a clean sport.
Oh, don't get it twisted. I think the Big 3 are all suspect as well at this point. We all want to believe they are just that great, but maybe they are getting extra help.
But Nadal has been an insanely conditioned athlete since his teens. I think genetics is on his side (Like his Uncle Miguel, a tireless defender for Barcelona). For all the speculation around him over the years, I think of all big 3, he was God gifted with incredible stamina.
Still, all the Big 3 do show signs of getting tired these days and needing more breaks, which is something. And they have enough money to afford the best legal recovery techniques. Djokovic actually takes his "Egg Chamber" with him to major tournaments to aid in recovery. It's legal, but most players will bankrupt themselves if they tried to transport a device like that to help them in tournaments.
Federer's stamina at his advanced age is pretty questionable, but like I said...we all want to believe.
