Serena's injury allowed Wozniacki to usurp her as No 1, thanks to the Dane's consistency, but at the grand slams a semi-final at the US Open was as good as it got for her last season.
Wozniacki must win in Australia to prove worth
The climax to 2010 in the women's game was blighted by the debate over whether Caroline Wozniacki was a worthy world No 1 after she overtook Serena Williams at the top of the rankings in October.
Williams won the Australian Open and Wimbledon and would have been a strong contender for the US Open had she not stepped on broken glass in early July, which curtailed her season as she required surgery on the problem.
To many people, myself included, she is comfortably the best women's player in the world right now. Her power and shot-making stand her out from the rest.
Her injury allowed Wozniacki to usurp her as No 1, thanks to the Dane's consistency and ability to win on the WTA Tour, although not at the grand slams where a semi-final at the US Open was as good as it got for her last year.
But the news that Williams's injury is so severe she will not be able to defend her Australian Open title next month means she is going to fall even further down the rankings from her No 4 spot, and leave her unable to fight for the top spot for quite a while.
Wozniacki is a good player but tennis is a result-based industry and the great players do their talking at the grand slam events.
The 20-year-old has yet to shine at the majors and she does not measure up to her title as the best player in the world.
Australia will be a great chance for her to put that right, otherwise the public will hanker for the return of Williams and, in their eyes, a worthy world No 1.