Analysis-Serena's impact to be felt long after pending retirement

Serena Williams announced her forthcoming retirement on Tuesday but even when her illustrious tennis career comes to a close her impact on the game she dominated for over two decades will be felt for generations to come.

Williams, who made her professional debut in 1995 a year after her older sister Venus, has been one of the game's most marketable stars. She has a slew of corporate partners and in 2019 became the first athlete to land on Forbes' list of America's richest self-made women.

The 40-year-old Williams, who is playing a U.S. Open tune-up event this week in Toronto, said in a Vogue article that she is "evolving away from tennis" and added in an Instagram post that "the countdown has begun."

Comparing players from different generations is somewhat of a lost cause given the countless ways to appraise achievements and analyse data but Williams is considered by many fans and pundits as the "GOAT" - a label that refers to the "Greatest Of All Time".

Williams revolutionised women's tennis with a lethal mix of powerful serves, groundstrokes and superb athleticism and became the most successful player in the Open Era by collecting 23 Grand Slam titles, the most recent coming in 2017.

That success also inspired a generation of tennis players, including Naomi Osaka who beat Williams in the 2018 U.S. Open final to claim the first of her four majors and remembers watching her childhood idol.

"When I was younger, the family event would be watching Serena and Venus," Osaka, who has Japanese and Haitian parents, said last week at a tournament in San Jose.

"So when I was watching that, that pushed me a lot. I never got to watch them play live, in a match, but I've gotten to watch their practices. Seeing that, seeing people that look