This is my problem with this reasoning. There are a shit load of AFL players running around doing nothing but running, jumping, and being hit in the air. Darren Jolly is 2.0m tall and 108kg, Sam Jacobs is 2.03m and 105kg, Nic Naitanui is 2.01m and 110kg - and those are just 3 names off the top of my head. There's no way you can convince me Manu does more jumping and getting knocked about in the air than AFL players, especially forwards and ruckmen.
So while I don't want to offend you or your experience(s), I'm going to assume that the above theory is your own, and isn't actually following any sort of research or sports science.
Manu has had a host of injuries, as have many of our current squad, as has almost every player involved in professional sport around the world. Perhaps you're applying a little too much from your own world/experience and trying to make it fit with a totally different profession.
Seriously..GAYFL FFS, appples and potatoes, you may as well have said soccer and basketball.