One of the reasons why soccer players have a hard time taking bumps and knocks is because it is VERY hard to stay balanced while using your strong foot to dribble the ball at the same time. As a soccer player, I rarely get knocked over playing defense. But when I have the ball it's a completely different story. Dribbling technique itself takes away your strong foot so it is rarely planted correctly. Add that I play on the wing and am often running at full sprint while trying to dribble... an easily timed tackle or bump will definitely send me off course or to the ground. That's why you see guys like Ronaldo flying everywhere. When he dribbles, his technique, which makes him a brilliant player nevertheless, forces him to take so many touches on the ball. He usually has a straight posture too, making his center of gravity that much higher and easy to knock over. People in other sports don't have to lend their feet to do anything other than move, so it's free to stabilize them more. People don't really point this out when they see soccer guys fall but it seems like it should be common sense.