(10) Caroline Wozniacki
The Dane began 2012 as world number one but soon lost that position when she bowed out of the Australian Open at the quarter-final stage.
Since then she slipped further down the rankings, not helped by a first-round exit at Wimbledon and at the US Open as she lost her place in the top 10.
Some will put this down to the constant questioning of her status as world number one by the press and public - like Dinara Safina and Jelena Jankovic before her, Wozniacki was top of the rankings for around a year without winning a grand slam title. Others will blame her relationship with golfer Rory McIlroy, whose success in the majors stands in contrast to his girlfriend.
Wozniacki, whose Polish father was a professional footballer, makes the most of a limited game, one which relies on defence.
She did finish 2012 strongly though by winning in Seoul and Moscow as she posted an 18-3 record post-Flushing Meadows to regain a place in the top 10 in November.