Serena Williams of the U.S. reacts during her match against Bethanie Mattek-Sands of the U.S. at the U.S. Open Championships tennis tournament in New York, September 4, 2015 (Reuters)
Serena Williams withdrew from her opening match at the Hopman Cup because of inflammation in her left knee, an early setback in preparations for her Australian Open title defense.
No. 1-ranked Williams practiced Monday ahead of her scheduled season-opener against Elina Svitolina of Ukraine in the international mixed-team competition at Perth Arena, but withdrew from the match and was replaced by Vicky Duval.
Duval lost 6-4, 6-1 to Svitolina and Alexandr Dolgopolov beat Jack Sock 6-4, 6-2 to clinch the best-of-three Group A match for Ukraine before the U.S. pair won the mixed doubles 6-2, 6-3.
Williams said she was confident she'd be able to join Sock in the U.S. team to play the Australia Gold team on Tuesday.
Hopman Cup tournament director Paul Kilderry said Williams reported feeling pain in her knee on Sunday.
''She wanted to give herself every chance to play, she warmed up this morning but common sense prevailed and she just thought today she can't do it,'' Kilderry said.
After winning the Australian and French Opens and Wimbledon titles in 2015 Williams had two months off after the U.S. Open, where she narrowly missed completing a season Grand Slam by losing to Roberta Vinci in the semifinals.
For the 20-year-old Duval, who returned to tennis in August after overcoming Hodgkin's lymphoma, filling in for Williams was a great opportunity.
''I was kind of nervous because I was filling in big shoes. But I had a really fun time today,'' Duval said. ''I have a whole new outlook on life. I'm just really grateful to be back and do what I love.''
At the Brisbane International, 2015 finalist Grigor Dimitrov needed six match points before beating fifth-seeded Gilles Simon 6-3, 7-6 (10) to move into the second round.
In women's singles, No. 6-seeded Carla Suarez Navarro advanced along with No. 7 Belinda Bencic, who beat Sara Errani 6-1, 6-2, and Vinci, who overcame former No. 1-ranked Jelena Jankovic 3-6, 6-2, 6-4.
At the ASB Classic in Auckland, New Zealand, fourth-seeded Svetlana Kuznetsova progressed to the second round, leading 6-2, 1-1 when Mona Barthel of Germany retired from their first-round match due to a stomach ailment.
Teenage Latvian wild card Jelena Ostapenko beat No. 56 Johanna Larsson of Sweden 6-1, 7-5 and could face second-seeded Ana Ivanovic in the second round.
The drawcards for the Auckland tournament, Venus Williams, Ivanovic and Caroline Wozniacki, are all drawn to play their opening matches on Tuesday.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)