I don't see what any of these previous few posts have to do with the semi final yesterday, but whatever....
Being healthy and being able to compete requires another skill necessary in tennis. It is easy to overplay and over extend oneself, but it takes some smarts to avoid any serious injuries. Most of tennis injuries are like that, a bit of soreness, it hurts a bit, but guys just keep pushing through until it is too late and they are damaged and have to stay off the tour for extended period of time. Everybody should know their limits and take it easy when they feel something is wrong with them.
I don't believe for a second that Nole, Federer, Berdych, Ferrer and some others are just somehow gifted and injury-proof. They work hard on their schedule and they know when they can push and when it is not the time for that. Being smart and playing within themselves is the main reason that these guys are relatively injury free.
Poor Janko for example, played with painful foot for months until it got so bad that he had to miss 17 months of his career and had 2 surgeries to remove tumors from it. Cilic served harder than ever in this past USO and his shoulder/back paid the price so he is not the same ever since. There are many cases like that. As much as I feel for Delpo, I am afraid he damaged his wrists also with going for too much on his shots for long period of time.
Unless it is a freak accident and there is no way to prevent it, unfortunately most of other injuries are just that - overplaying and not knowing their limits.