Still, there were signs towards the end of 2016 that she was heading in the right direction again, Wozniacki reaching the semi-finals of the US Open - a tournament she has twice finished runner-up at. She also won WTA titles in Tokyo and Hong Kong.
At the Australian Open, making the last four in 2011 has been her best effort.
The following year she lost in the quarter-finals and duly conceded her top ranking and has never regained it.
Wozniacki has tried to add more aggression to her naturally defensive game but others on the tour have more power.
The 26-year-old is another WTA star with sport in the genes - her father Piotr (who is also her coach) was a Polish professional footballer, whose career took him to Denmark, while her mother represented Poland in volleyball.