Naomi Osaka apologised after a troublesome back injury forced her to withdraw from the Hong Kong Open and cut her comeback season short.

The four-time major champion was expected to feature in the final WTA 500 event of the year but has pulled out, still citing an injury she suffered in the China Open against Coco Gauff this month.

Osaka has posted a 22-17 record since returning from maternity leave, but her comeback campaign was confirmed to have hit an abrupt end on Monday.

"I'm really sorry that I have had to withdraw from competing at the Prudential Hong Kong Tennis Open and the rest of this tennis season," said Osaka.

"I love visiting the tournament and, despite the obvious disappointment of not being able to play, I want to reassure all my wonderful Hong Kong fans that I will still be attending the event.

"I am very much looking forward to meeting you all.  

"There is a wonderful line-up of world-class players coming to the tournament and I want to wish them all the best of luck in this exciting event."

Osaka racked up six victories over top-20 opponents this year, including her first win over a top-10 opponent in two years by beating Jelena Ostapenko in the first round of the US Open.

Peter Johnston, the director of International Events at the Hong Kong, China Tennis Association, offered his well-wishes to Osaka despite her withdrawal.

"We are obviously very disappointed that Naomi has had to withdraw from competing, and we sincerely hope that she makes a speedy recovery from her injuries," he said.

"We are nevertheless confident that we have a stellar field of world-class players to enthuse and excite Hong Kong tennis fans."