Angelique Kerber will have to hold on to No 2 spot, as her failure to beat Karolina Pliskova ensures Williams remains at the top.
Serenea Williams has spent 183 weeks at the top of the WTA rankings, and will continue to do so due to the German’s 6-3, 6-1 loss to the Czech star.
Williams withdrew from the tournament with a shoulder injury on Monday.
Kerber, who would be the first German to top the world rankings since Graf, said: “If someday it happens, it happens, but I will not be making too much pressure on this. I’ve had such a great year so far and it’s not over yet.”
It was Pliskova’s first victory in a final against Kerber at the third attempt.
The Australian Open champion, was broken five times in the match and only managed one of her own as she fell to her third defeat to Pliskova.