I think the main problem with soccer is that "heading" the ball is a crucial part of the game. The difficulty with all contact sports is that they involve, well, contact. Even in a friendly match of basketball, hockey etc... bumping is inevitable and trips and falls quite likely.

You could bounce the ball around on your foot, but the moment you started to pass the ball or, God forbid, scrimage, you'd be at risk. Besides, dribbling the ball, but not playing, would probably seem pointless and boring.

I agree with the others that you need to think about sports that are less risky. You've already had some excellent suggestion like yoga and tai chi.

Of course, those things will keep you fit, but they may lack the competitive character you enjoy. In that case, do you golf? It's challenging, but the risk level is more acceptable. Bowling, cross-country skiing, snowshoeing and swimming may also be acceptable alternatives.