Naomi Osaka stepped up the defence of her Australian Open title with a composed beating of Madison Brengle on Wednesday to move a step closer to a blockbuster clash with top seed Ashleigh Barty.

The 1-6, 6-3, 6-4 defeat of Caroline Wozniacki, the Danish third seed and former world number one, eliminated the last of the WTA Auckland Classic drawcards, a day after the exit of the two top seeds Serena and Venus Williams.

Top seeded Serena Williams was sent packing 6-4, 6-7 (7/3), 6-4 in a two-hour, 14-minute match against the world number 72 Madison Brengle in the second round of the WTA Auckland Classic

Italy's Sara Errani had to fight it out against Madison Brengle 4-6, 6-1, 6-4 to set up semi-final clash against Caroline Garcia.

Karolina Pliskova has played four WTA finals this year and won one of them - in Seoul last month.