Organizers announced Monday that Williams, No. 2 in the rankings, would not recover in time after she was injured at last month's WTA Championships. The Hopman Cup starts Jan. 3 but Williams still intends to play at the Australian Open starting Jan. 19.
Two-time champion James Blake will now be joined by Meghann Shaughnessy on the U.S. team in the mixed-team tournament. Williams and Blake combined to win the 2003 Hopman Cup.