Doha: World Number one and two-time Grand Slam winner Naomi Osaka has pulled out of next week's Qatar Open because of a back injury, tournament organisers said on Tuesday.
No more details were given about the injury but Osaka, 21, also withdrew from the Hong Kong Open last October because of problems with her back.
"I am sorry to have withdraw from Doha this year as I was looking forward to playing and seeing my fans there," said Osaka, who won the Australian Open last month, in the statement.
"I wish everyone a great week and hope to see everyone next year."
Her withdrawal will come as a blow to organisers in Doha, who also announced on Tuesday that her place as top seed in the Qatar Open will be taken by the woman she recently replaced as world number one, Romania's Simona Halep.
Japanese Osaka is currently the US Open and Australian Open champion.
She beat Czech star Petra Kvitova -- last year's Qatar Open winner -- in three sets in Melbourne to claim her second Grand Slam after upsetting Serena Williams at Flushing Meadows for her first one.