speaking as someone who is not that experienced with the game and playing in lower levels, I feel that GK are as important as any other player on the field. I have had 6 clean sheets in a row mainly because of GKs, at least in two of the games...Of course just like the real life, a great keeper will look weak when his or Defense is weak, but in close games, you see how GK make a difference. Good luck to you.