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Top-ranked Serena Williams retired during the second set of her Hopman Cup match in Perth yesterday, culminating a day of injuries and upsets for the leading players on the women's tour less than two week from the Australian Open.

Williams, who missed the U.S. team's opening loss to Ukraine on Monday because of inflammation in her left knee, was trailing 7-5, 2-1 against Jarmila Wolfe when she left the court.

Australia now has a 1-0 lead ahead of the men's singles in a Group A match at the international mixed team tournament. Ukraine improved to 2-0 in the group with a win over Czech Republic.

Earlier, defending champion Maria Sharapova and top-seeded Simona Halep withdrew from the Brisbane International with injuries within an hour of each other, without playing a match. At the ASB Classic in Auckland, New Zealand, defending champion Venus Williams and 2014 winner Ana Ivanovic were ousted in first-round upsets.

No. 4-ranked Sharapova was scheduled to play fellow Russian Ekaterina Makarova but withdrew hours before the first-round match rather than risk further damage to a sore left forearm ahead of the first Grand Slam tournament of the season.

The five-time major winner said she'd hurt her forearm in practice and had to withdraw as a precaution. Her place in the draw was taken by Margarita Gasparyan, who lost to Makarova. — AP