That's not bad luck, that's his poor forehand technique (wrist injury) and his massive height to weight imbalance that makes him prone to injuries in a sport where you have to change directions quickly, sprint, stop and lunge. For example Raonic injured his hip due to a freak fall, that is what's classified as "bad luck". Poor technique and trying to defend when you are 198cm tall is a recipe for disaster.
Since when is Del Potro's FH technique poor
? Not to mention that'd not explain why his left
wrist was injured during the American hardcourt season.