Ashleigh Barty has been denied the chance to defend her season-ending championship following the cancellation of 11 tournaments planned for China in October and November, including the WTA Finals.
Seven women's events and four men's, including the showpiece eight-woman season finale in Shenzhen, have falled victim to the coronavirus pandemic.
Rather than try to move or reschedule any of those events, the WTA and ATP tours announced they were scrapping all of them after China's General Administration of Sport said the country would not host any international sporting events for the rest of this year because of the COVID-19 outbreak.
"We are extremely disappointed that our world-class events in China will not take place this year," WTA Chairman Steve Simon said.
"We do, however, respect the decision that has been made and and are eager to return to China as soon as possible next season."
His group called off seven women's tournaments also including the China Open and WTA Elite Trophy, which Barty won in 2018 to spark her incredible run to world No.1.
The ATP wiped four men's events, including its only Masters 1000 tournament in Asia.
"Our approach throughout this pandemic has been to always follow local guidance when staging events," ATP Chairman Andrea Gaudenzi said.
"We respect the Chinese government's decision to do what's best for the country in response to the unprecedented global situation.
"It's with a heavy heart that we announce ATP tournaments will not be played in China this year."
The men's tour said it would continue to try to work on arranging a tour calendar for the latter stages of this year, including the ATP Finals scheduled for November.
All sanctioned tennis has been on hold since March because of the pandemic, and both tours are tentatively planning to resume in August. This week, though, the ATP cancelled its tournament that was slated for Washington, with qualifying to begin on August 13.
The WTA still intends to return to action in Palermo, Italy, on August 3, but Barty has yet to reveal when she plans on returning to the tour.
The Australian pocketed $US4.42 million - the biggest cheque in tennis history - for reigning in Shenzhen last November, just weeks before the first coronavirus outbreak in nearby Wuhan.
The next scheduled grand slam tournament is the US Open, which is supposed to start in New York on August 31, while the French Open, which Barty also won last year, has been postponed from May to late September.