Yesterday, Williams played only her second singles match since she returned to action at Wimbledon in June after a year-long absence from competition, beating Spain's Nuria Parrizas Diaz to reach the second round of the Toronto Open.
But the 40-year-old said after the match that she could see the light at the end of the tennis tunnel in her career.
"I have never liked the word retirement," Williams wrote in a Vogue article.
"Maybe the best word to describe what I'm up to is evolution. I'm here to tell you that I'm evolving away from tennis, toward other things that are important to me.
"A few years ago I quietly started Serena Ventures, a venture capital firm. Soon after that, I started a family. I want to grow that family."
Williams won her last Grand Slam in 2017 and has been chasing an elusive 24th crown that would draw her level with Australian Margaret Court who holds the record for the most majors.
She came tantalisingly close to achieving that feat, featuring in four major finals since giving birth to daughter Olympia in 2017.
"There are people who say I'm not the GOAT (greatest of all time) because I didn't pass Court's record, which she achieved before the 'Open era' that began in 1968," said former world number one Williams, who sought the advice of her friend Tiger Woods before picking up a racket again this spring.
"I'd be lying if I said I didn't want that record. Obviously I do. But day to day, I'm really not thinking about her."
Williams later said in an Instagram post that it was time to move in a "different direction."
"The countdown has begun. I have to focus on being a mom, my spiritual goals and finally discovering a different, but just exciting Serena."
Williams announced herself on the grandest stage by winning the 1999 U.S. Open, a tournament she would go on to claim five more times.
In a storied career during which she dominated rivals like no other athlete, she also claimed seven Australian Open titles, three French Open titles and seven Wimbledon crowns.