The Madrid Open Virtual Pro got underway on Monday, with Rafael Nadal and Andy Murray in action.
Coco Gauff claimed another famous scalp in defending champion Naomi Osaka, as Serena Williams also suffered a shock defeat.
Caroline Wozniacki's career came to an end following the 29-year-old's third-round loss to Ons Jabeur in Melbourne on Friday.
A third-round loss at the Australian Open brought an end to Caroline Wozniacki's professional career.
It was a good day for the favourites in the women's draw at the Australian Open, with Ash Barty and Serena Williams winning through.
The world's top women got the job done on Monday, with Ash Barty joining Naomi Osaka and Serena Williams in round two in Melbourne.
Caroline Wozniacki and Serena Williams saw their Auckland Open title hopes collapse with a surprise defeat in the final.
Serena Williams needed just 44 minutes to brush past Amanda Anisimova in the Auckland Open semi-finals.
Ash Barty shuffered a shock loss in Brisbane but Serena Williams and Naomi Osaka overcame scares ahead of the Australian Open.
It has been a long time coming, but best friends off court Serena Williams and Caroline Wozniacki have shown on-court chemistry in Auckland.