Since Agassi is guaranteed into Shanghai

I don't think he will go.

He won't play.

It's hard to take anything out of Agassi's form in this tournament, he beat some good players but also was spotty, I think a lot of stars aligned for him to get to the final, but still I think his form is good enough to defeat 90% of the players out there. In big matches he can come through, if Safin and Hewitt won't go then a couple of the clay courters will fill in and those are guaranteed wins. In such a scenerio, I see him making the semis (if he meets Rogi) or the final since Hewitt, Roddick and Nadal are favourable matchups for him.

If he withdraws from Madrid, he won't go

With his back/nerve problem, I don't think he will play any matches after this USO. At 2002, he merely showed up in Shanghai and packed his bag after 2 matches, didn't even bother to finish the last in RR.

I'm not sure if he will go or not. I'm not sure what he wants to do for next year. If he does stay healthy, he is better than just about everybody on tour on a hardcourt and would bea tough out at the AO next year.

He'll rest for the AO.

This could be his last year-end championship. Who knows what form he could have next year so I think he will go. And the new stadium is a plus.

Is he guaranteed? Who else is guaranteed and how many spots are open?

I know Fed and Rafa are mathematically gauranteed. Don't think anyone else is.

Safin is guaranteed if he is fit enough to take his place.