World number one Ashleigh Barty remains upbeat about her Australian Open preparations despite losing her opening match of the season at the Brisbane International on Thursday.
American qualifier Jennifer Brady notched up her first-ever win over a top-10 player when she beat Barty 6-4, 7-6 (7/4) at the Pat Rafter Arena.
Barty conceded afterwards she had simply been outplayed by Brady, who also beat former world number one Maria Sharapova in the first round.
Brady will now play two-time Wimbledon champion Czech Republic’s Petra Kvitova, who beat Russian qualifier Liudmila Samsonova 6-3, 6-2.
Karolina Pliskova, the world number two and defending champion, had to battle for two hours to avoid the same fate as Barty, eventually beating Australian wildcard Ajla Tomljanovic 6-4, 6-7 (5/7), 6-1.
Pliskova will meet Alison Riske of the United States in the quarter-finals.
Third seed Naomi Osaka was taken to three sets for the second match in a row before eventually overcoming the USA’s Sofia Kenin.
Kenin won the first set in a tiebreak before Osaka took control, winning 6-7 (3/7), 6-3, 6-1.
Osaka will play sixth seed Kiki Bertens in the quarter-finals after the Dutchwoman beat Estonia’s Anett Kontaveit 6-3, 2-6, 7-5.