Williams has been one of the most successful Olympians in tennis, winning gold medals in doubles with her 41-year-old sister, Venus, in 2000, 2008 and 2012.
For Christopher Clarey's latest contributions to The Japan Times, see below:
Naomi Osaka, a superstar in the sport, pulled out of the French Open after she was fined for skipping a news conference. Did it have to end this way?
The surprisingly stern warning was delivered in a statement signed by the leaders of the four Grand Slam tournaments.