Top seed Serena Williams powered into the semi-finals of the Australian Open yesterday, but was denied a showdown with elder sister Venus in Melbourne.

Serena had to save set points in her second-round match and lost the opening set in rounds three and four, but made no such mistake against 2014 finalist Dominika Cibulkova.

The 18-time Grand Slam singles winner took the opening set with two breaks of serve and fired down a total of 15 aces to complete a 6-2 6-2 victory in 65 minutes. Venus had earlier lost in three sets to Madison Keys, a player 15 years her junior.

“I knew I had to be good today because she was in the final and plays really well on this court and I’m just happy to be through,” Serena said in an on-court interview which had to be cut short due to a cough she has been struggling with for the last few days.

Williams later said in her post-match conference she could be suffering from the virus which has seen Varvara Lepchenko taken to hospital twice in the past few days.

“I’ve felt better, but I’m feeling OK,” Serena said. “I’m just happy to still be in the tournament.”

Williams was set to face Keys in the semi-final starting in the early hours of this morning, while the other semi-final was due to be an all-Russian affair with Maria Sharapova and Ekaterina Makarova.

Meanwhile in the men’s singles Novak Djokovic was due to face defending champion Stan Wawrinka, with Andy Murray facing off against Tomas Berdych.

“It’s a great opportunity for both of them,” Berdych’s coach and former Murray assistant coach Dani Vallverdu said. “It was always going to happen and it’s great it happened early.”