Wozniacki digs deep to purge problems

Caroline Wozniacki's sunny smile has never masked her deep determination, and the Dane has needed all of her grit to turn around the toughest season of her career.

She'll be hoping that a 6-4, 6-4 upset of 2004 champion Svetlana Kuznetsova in the second round of the US Open on Wednesday is a turning point in a 2016 campaign marred by injury and a precipitous drop in ranking.

Wozniacki, a former world No 1, was two breaks down at 0-4 in the first set but won 12 of the next 16 games to advance.