The WTA's heat rule is in effect at the U.S. Open, allowing female players a break between the second and third sets.
Hsieh Su-Wei, who reached a career singles high ranking of 23 in 2013, welcomed the shake-up at the top of the sport.
The 36-year-old Serena now cannot meet a top 32 player until the semi-finals after the scattering of the seeds this week.
Wozniacki was left feeling a little croaky after going through the roller-coaster of her homeland's second round knock-out match with Croatia.
Caroline Wozniacki had to battle hard to book her place in the quarter-finals at the Eastbourne WTA tournament.
The Danish number two seed somehow prevailed after a titanic struggle 3-6, 6-2, 7-5 against the world number 119 on a searing Rod Laver Arena in two hours and 31 minutes.
Although beaten 6-4, 7-6 Julia Goerges in the Auckland final, Wozniacki said her preparation for Melbourne was on track.
Julia Goerges stunned top seed Caroline Wozniacki with a straight sets win in the WTA Auckland Classic final on Sunday.
Caroline Wozniacki won 10 straight games to continue a trend of one-sided matches at the Singapore Indoor Stadium.
World number two Simona Halep was booted out of the Wuhan Open 6-2, 6-1 by Russia's Daria Kasatkina on Tuesday.
Wozniacki posted her first career win over a number-one player in seven tries as she blasted eight aces in the two-hour.
Organisers said Caroline Wozniacki and Ana Ivanovic will compete at the Auckland Classic in January.