Karolina Pliskova has saved four match points to send seven-times champion Serena Williams crashing out of the Australian Open.

Seventh-seeded Pliskova rallied from 5-1 down in a tense deciding set to advance to her first semi-final at Melbourne Park with a 6-4 4-6 7-5 victory over the American on Wednesday.

The Czech will play Japanese fourth seed and reigning US Open champion Naomi Osaka in Thursday’s semi-finals, while Williams remains stranded one grand slam shy of Margaret Court’s all-time record 24 major singles titles.