Highlights from day nine at the Australian Open

Petra Kvitova reached her first grand slam semi-final since the stabbing two years ago that almost ended her career.

The Czech continued her impressive progress through the draw by taking out Australian hope Ashleigh Barty and next faces American debutante Danielle Collins, who won the battle of the unseeded players against Anastasia Pavlyuchenkova.

Stefanos Tsitsipas backed up his stunning win over Roger Federer by seeing off Roberto Bautista Agut and next faces Rafael Nadal, who is yet to drop a set and raced past Frances Tiafoe.

Tweet of the day

Picture of the day

Screen star

What could be more next generation than using your on-court interview to promote your YouTube channel? It certainly worked for Tsitsipas, who seemed almost as happy to see his number of subscribers more than double as he was to reach the semi-finals.

Explaining why he loves making travel vlogs, the Greek said: "When I'm desperate sometimes, when I feel down, I do these videos, I actually feel better. It makes me realise that tennis is not the most important thing in life, that we all have some other talents that we don't know about."

Letdown for teen

Various efforts to speed up tennis have been trialled over the past couple of years and, for the juniors at this year's tournament, that means playing on if a serve hits the top of the net. Unfortunately, and somewhat embarrassingly, for leading Australian hope Rinky Hijikata, the new rule slipped his mind when he was down match point to America's Zane Khan.

Who's up next?

Serena Williams continues her bid for a record-equalling 24th grand slam singles title when she faces Czech Karolina Pliskova in the quarter-finals.

Pliskova is still in the race to finish the tournament as world number one along with Naomi Osaka and Elina Svitolina, who meet in the other last-eight clash in the top half.

Novak Djokovic will hope to avoid another late night against marathon man Kei Nishikori while Milos Raonic takes on Frenchman Lucas Pouille.