World number three Naomi Osaka joined Serena Williams and Simona Halep with injury concerns ahead of the Australian Open Saturday as defending champion Sofia Kenin blamed her groin strain on spending two weeks in coronavirus quarantine.

Japan’s Osaka, the US Open champion and 2019 Australian Open winner, was set to play Elise Mertens in the Gippsland Trophy semi-final but withdrew.

“Sorry to Tennis Australia and the fans to have to withdraw today,” she said on the WTA’s Twitter account.

“I have a niggling injury and in light of the AO (Australian Open) on the horizon I need to be cautious. I look forward to competing next week.”

Osaka had looked in fine form powering past Irina-Camelia Begu 7-5, 6-1 in 76 minutes on Friday.

She joined Williams as a late withdrawal after the American 23-time Grand Slam winner pulled out of her semi-final clash against world number one Ashleigh Barty with a shoulder problem Friday.

Williams, 39, had ousted fellow American Danielle Collins 6-2, 4-6, 10-6 in the Yarra Valley Classic but withdrew hours later, despite showing no ill effects during the match.

‘Completely sore’

Spanish world number two Rafael Nadal has also been struggling, with a lower back niggle again keeping him out of the ATP Cup on Saturday.

Two-time Australian Open champion Victoria Azarenka was another casualty, opting not to play her quarter-final clash with Anett Kontaveit at the Grampians Trophy due to a lower-back injury.

World number four Kenin said not being able to practise properly during quarantine had left her “completely sore” after returning to action.

Due to Australia’s strict rules for incoming travellers, players underwent a compulsory 14-day quarantine on arrival but were granted daily five-hour blocks for training and treatment.

Some players, including Azarenka, had to endure a hard lockdown and were not able to train at all after coronavirus cases were detected on their charter flights.

“After two matches, my leg is completely sore,” said Kenin. “You can see that being in a room for two weeks, not playing, practising, it’s not the same as playing a match clearly.

“People who haven’t played matches for two weeks, it’s obviously not the same.”

The American added that she hoped to be fit and firing when the Grand Slam starts on Monday.

“Today it’s better. I’m not going to complain about that,” she said. “I want it to be better for the Australian Open.”

While Williams and Osaka’s withdrawals appear precautionary, there might be more concern over the fitness of world number two Simona Halep.

She was thrashed by Ekaterina Alexandrova 6-2, 6-1 in the Gippsland Trophy quarter-finals, where she appeared hampered by a lower-back injury.

Halep strapped on a back brace after calling for medical attention after the first set in a lopsided contest lasting just one hour.