Serena Williams has announced her withdrawal from next month’s Australian Open, extending her absence from the sport that she long ruled.

“I am not where I need to be physically to compete,” Williams said in an announcement on Wednesday as the Australian Open released the list of entered players for the 2022 tournament.

Williams, a seven-time Australian Open singles champion, is now 40 years old and has not played on the WTA Tour since June 28, when she retired late in the first set of her opening round match at Wimbledon because of an injured right hamstring.

The injury was slow to heal, and it also kept Williams from competing in this year’s United States Open. Williams did not mention the hamstring injury specifically in her statement on Wednesday, saying only that she had decided to withdraw because of “the advice from my medical team.”

While Williams confirmed her absence, the Australian Open said that Novak Djokovic, the No. 1 men’s singles player, was entered in the event, which is set to begin on Jan. 17 in Melbourne.

The state government of Victoria is requiring that all players be fully vaccinated to compete, and Djokovic has declined in recent weeks to reveal his vaccination status or confirm if he would play in the Australian Open, where he has won nine singles titles. But he is on the entry list, only a week after his father decried the vaccination requirement as “these blackmails and conditions” and suggested his son would not play.

Williams said she was “excited to return and compete at my highest level,” but it is unclear when or if she will be able to achieve that goal.

Williams, ranked 41st, has not won a Grand Slam singles title in nearly four years: She captured the Australian Open in January 2017 when she was two months pregnant with her daughter, Olympia. She returned to the tour in 2018 after Olympia’s birth and remarkably reached the singles finals at Wimbledon and the United States Open in 2018 and again in 2019.

But though she won her only tour title since her comeback in January 2020 in Auckland, New Zealand, she has struggled to sustain momentum. She has shown flashes of strong form, returning after the tour’s five-month pandemic hiatus in 2020 to reach the semifinals of the U.S. Open, where she lost a taut three-set duel against Victoria Azarenka. At this year’s Australian Open in February, Williams arrived in Melbourne in excellent physical condition and was impressive in the early rounds but was defeated in straight sets by Naomi Osaka in the semifinals.

The Australian Open has been the scene of some of Williams’s greatest successes. In 2003, she won her fourth straight Grand Slam singles title in Melbourne. In 2005, she saved three match points in the semifinals in a classic match against Maria Sharapova and went on to beat Lindsay Davenport in the final. In 2007, she came into the tournament unseeded and swept to the title. In 2017, she won while pregnant without dropping a set.

But it is now unclear if she will return to the tournament where she has won seven of her 23 Grand Slam singles titles: one short of Margaret Court’s record.