Top seeds Roger Federer and Serena Williams needed all their fighting qualities to stay in the Australian tennis Open on Tuesday, while 2008 champion Novak Djokovic was beaten in the late match.
Federer reeled off 13 games in a row to dig himself out of trouble and beat Russia's Nikolay Davydenko in four sets in a wildly fluctuating match, making it 23 consecutive grand slam semi-finals for the Swiss world number one.
Serena was also staring down the barrel in her quarter-final against Victoria Azarenka of Belarus before she recovered to win in three.
Li Na beat Venus Williams to give China two semi-finalists in the women's draw.
Federer's next opponent will be Jo-Wilfried Tsonga after the Frenchman beat Djokovic in five to avenge his loss to the Serb in the 2008 Australian final.
Djokovic was heavily criticised after he retired with heat exhaustion while trying to defend his title last year and the world number three said he was sick again against Tsonga.