Serena Williams suffers Australian Open setback after pulling out of Hopman Cup match with knee injury

Serena Williams' preparation for the Australian Open has suffered an early setback after a knee problem forced her to pull out of her opening match of the Hopman Cup. The world no. 1 was scheduled to take on Elina Svitolina in United States' opening encounter on 4 January, but pulled up during a practise session.

The 34-year-old, however, says she will be ready in time to play in the next round of the mixed-teams competition in Perth against Australia's Lleyton Hewitt and Jarmila Wolfe on 5 January.

Serena dominated the women's singles division in 2015, winning three of the four grand slams and only being denied a clean sweep at the US Open after suffering a semi-final defeat to Roberta Vinci.

The veteran American took the rest of the year off following that loss, withdrawing from the China Open and the WTA finals in Singapore.

It was during that period that her coach Patrick Mouratoglou suggested she was dealing with the same injury woes that have plagued Rafael Nadal in the last two years.

"It's just playing for so many years, the cartilage is [almost] gone," Mouratoglou said.

"Not all of it, but a big part, so the bones just hit themselves. She has bone bruises, and if you keep on playing with this for too long, too much, the next step is a stress fracture."