Assuming it's the same controls as Rugby Challenge 1, you get used to it pretty quickly. It just takes a bit of an adjustment at the beginning while you get used to things, especially if you are used to Rugby 08 controls.
I am having the same frustrations as the OP.. I have hardly won one match in this game playing on keyboard, when I try to fend, I end up pressing D instead of F.. Somehow I think it will be much better with a gamepad. Anyone here moved from keyboard to controller? Also what is your take on this?