Williams has lost just one match since a first-round shocker at the French Open last May, sweeping titles at Wimbledon, the US Open, the Olympics and the WTA Championships on her way to a stunning season finish.
But the 31-year-old’s lack of tournaments in 2012 left Williams with 9400 ranking points, behind world No.1 Victoria Azarenka (10,595) and No.2 Maria Sharapova (10,045).
Williams must win the Australian Open next month to absolutely guarantee a return to the world No.1 ranking – a feat which would make her the oldest player ever to hold the top ranking.
Stosur rates Williams as the one to beat this coming summer and the Brisbane International could be the first step towards Williams putting the world rankings back in their rightful order.
“I think it’s very hard going against (Serena) as No.1 at the moment,” Stosur said.
“Obviously she is not No.1 on paper, but I think having won two Grand Slams, the Olympics and the end of year championships, I think that pretty much qualifies you as being in that spot.”