Casey Dellacqua is into the quarter-finals of the WTA Tour’s Pan Pacific Open but fellow Australian Jarmila Gajdosova fell to second-seeded Caroline Wozniacki of Denmark 4-6 7-5 6-3.

The former world number, playing in her first match since losing in the US Open final, needed two hours and 11 minutes to oust qualifier Gajdosova and book a quarter-final spot against Spain’s Carla Suarez Navarro.

“She was playing very well. I was trying to fight for every point and it took me a little while just get into it,” said Wozniacki.

“She was hitting a very heavy ball. I was playing a little bit too short and that gave Jarmila opportunities to play very aggressive.”

Wozniacki lost the US Open final 6-3 6-3 to top-ranked American Serena Williams at Flushing Meadows two weeks ago.

Gajdosova, ranked 91st in the world, who has never won in her previous six matches with Wozniacki, broke her serve in their opening game. But the Dane immediately broke her back.

The 27-year-old Australian surged to 5-4 by breaking the Dane after five deuces and keeping her next serve to take the first set.

The two players broke each other early in the second set and went tit-for-tat until Gajdosova lost her serve with erratic shots in the 12th game.

After losing her serve at the start of the decisive set, Wozniacki broke the Australian three times and yield no point in the ninth game, banging in a two-handed backhand across the court on match point.

In earlier second-round matches Dellacqua trounced New Zealand’s Marina Erakovic 6-2 6-4 and eighth-seeded Suarez Navarro beat Russian qualifier Daria Gavrilova 7-6 (7-5) 6-3.

Spaniard Garbine Muguruza upset fourth-seeded Jelena Jankovic of Serbia 7-6 (7-4) 6-4 in almost two hours.

Dellacqua and Muguruza will clash in the quarter-finals on Wozniacki’s side of the draw with Germany’s world number-eight Angelique Kerber heading the other half as the top seed.