This posture is great for stretching EVERY part of the body! No sports person should be without this in their stretch routines.
Downward facing dog is great for releasing tension and stretching out the calves, back and shoulders and perhaps most importantly the hamstrings, which can be very tight for some sports-people, so this is a big one to help prevent injuries.
It's great for after training or a game.
This is also a good one for people who work with a computer for long periods or have to stand up all day.
If you have any injuries in your hips, knees or back then you need to be careful.