On the flip side, the likes of Ma'a Nonu and Conrad Smith have been able to survive almost 10 seasons each in the midfield - suffering only occasional injuries. They have absorbed the constant battering and, even though both are in their 30s, they are not showing obvious signs of wear and tear.
So maybe Kahui is right - maybe he is just unlucky. "I feel like a big part of my role is to be physical and to get over the gain line and act like a loose forward so there are times when it can be particularly physical," he says. "The game is faster and the boys are obviously bigger.
"I know when I started I was 96kg and now I'm 103kg. That's the way the game is going - harder and faster, especially when you have to go to South Africa a couple of times a year, you certainly end up knowing there are some big men playing in this competition.
"But I think I'm just unlucky. If you look at my last [serious] injury, that was someone falling on my back. Injuries are going to happen and you do what you can to avoid them - you do your pre-hab and rehab right, but there are times when things go wrong: when someone lands on your leg or whatever."