Caroline Wozniacki’s hoodoo at the Sydney International has continued with a marathon three-set loss in stifling heat.

The former world No.1 was attempting to end a run of seven Sydney visits without getting past the quarter-final stage, but eventually fell 7-5 6-7 (7-6) 6-4 to Barbora Strycova.

Almost a third of the three-hour, 19-minute epic was played in over 40-degree heat.

Both players were treated for foot injuries during a gruelling second set on Ken Rosewall Arena, where they also battled mental demons under the Sydney heatwave.

Wozniacki looked on track to end her barren run at Homebush when she battled back from 5-2 down in the second set, and then 5-0 in the tiebreaker, to force a third set.

But the world No.19 Strycova denied the Dane.

The Czech is the first woman through to the semi-finals on day four and will now meet the winner of second-seed Agnieszka Radwanska and qualifier Ying-Ting Duan.

The winner of Eugenie Bouchard and Anastasia Pavlyuchenkova will face the other victor between Daria Kasatkina and Johanna Konta.