Serena Williams won't be chasing a 24th Grand Slam singles title at the US Open, but with her 40th birthday only a month away, she will be starting perhaps her greatest challenge in closing out her career on her own terms.

Williams revealed Wednesday she would miss the New York hardcourt showdown with a torn right hamstring suffered in a first-round match last month at Wimbledon.

"After careful consideration and following the advice of my doctors and medical team, I have decided to withdraw from the US Open to allow my body to heal completely from a torn hamstring," Williams posted on Instagram.

Williams, whose 23 Grand Slam singles crowns are one shy of Margaret Court's all-time record, will be battling back from injury at an age when most players have retired.

The American star is already the oldest woman to win a Grand Slam singles crown, taking the 2018 Australian Open title at age 35 while pregnant before taking a year off to give birth to daughter Olympia.

She suffered a pulmonary embolism after delivery and was bed-ridden for six weeks but battled back to world-class form, reaching the 2018 and 2019 finals at Wimbledon and the US Open, and until now hadn't missed a Grand Slam start since her motherhood hiatus.

Williams failed to take a set in any of the four trophy matches, the last in New York just shy of her 38th birthday making her the oldest female finalist in Grand Slam singles history.

Ken Rosewall was 37 when he became the oldest Grand Slam singles winner and 39 when he reached the 1974 US Open final. If Serena should reach another Slam singles final, she would become the oldest man or woman to do so.

"I feel like people can play longer," Williams said at Wimbledon. "Technology has played a huge role in that -- the way we view the game, the way we recover, the way our shoes are made, the way the equipment is made.

"Because normally people retire at 29, 30 -- before 29, 30, 32 was the max. I feel like there are several players at that age who are just hitting their stride."

Williams won 10 Grand Slam titles in her 30s, taking each crown at least twice, and was a runner-up six more times, at least once in all four events.

Whether or not Williams ever matches Court's record, many consider her the greatest women's tennis player ever.

"Either way she's the greatest female player in my book that has ever played, one of the greatest athletes, period, that has ever played," said US legend John McEnroe.

The woman who began playing against older sister Venus under the guidance of her father Richard has won seven Australian Open and seven Wimbledon titles, three French Opens and six US Open crowns, including her first at age 17 at Arthur Ashe Stadium in 1999.

She lost to Victoria Azarenka in last year's US Open semi-finals and fell to Naomi Osaka in this year's Australian Open semi-finals.

For more than two decades, Williams has faced new generations of rivals who raised their games whenever she was across the net from them.

"It has definitely made me better," Williams said. "I've had a big X on my back since '99, since I won the US Open. When players play me that hard every single tournament, every single match, every single Grand Slam, it just doesn't matter where, you just get better."

Williams said she was "heartbroken" when she was forced to leave the court at Wimbledon injured, her spirits lifted by a cheering crowd who were hoping they hadn't watched her final bow at Centre Court.

"Serena Williams has been fully committed to her recovery and we've done everything we could," tweeted Williams coach Patrick Mouratoglou. "But her body isn't ready. It is heartbreaking, but this is the only possible decision."

Williams has played a minimal schedule most seasons to help her longevity.

"Playing the way I played helped my career," she said. "I don't think I could have played as long if I had to play a lot of weeks. You just have to figure out what works for you and go with it."