• Sharapova forced to retire from Shenzhen Open quarter-final • First grand slam of the year begins on 14 January

Maria Sharapova is a doubt for this year’s Australian Open after being forced to retire from her Shenzhen Open quarter-final match against Aryna Sabalenka with a thigh injury.

The former world No 1 struggled to move on court and conceded the opening set 6-1, with coach Thomas Hogstedt urging the Russian to take her game to the next level or call for a medical timeout. “If you feel more like you did on the first point, then you just stop. Or you take a medical now,” he said. “But the shots are there … you have to get it up to another gear.”

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Sharapova now faces a race against time to compete in the first grand slam of the year, which begins in Melbourne on 14 January.

Sharapova, who won the Australian Open in 2008, won the Tianjin Open in 2017 after a 15-month doping suspension but has endured a difficult run at the slams. A quarter-final appearance at the French Open last year gave reasons for optimism but early exits at Wimbledon and the US Open showed her game lacked the sharpness to compete at the highest level.