“Like I said in the article, I’m terrible at goodbyes. But goodbye, Toronto,” she said in an on-court interview after the game.
Together with her older sister Venus, she helped change the sport, regularly winning Grand Slams in both singles and doubles tennis.
The 40-year-old has 73 singles titles, 23 doubles titles and two mixed doubles titles including 39 Grand Slam titles – 23 singles titles, 14 doubles titles and two mixed doubles titles.
“There was a lot of emotion, obviously,” Williams told the audience about the match.
“I love to play here, I have always loved to play here. I wish I could have played better but Belinda played really well today. It was 24 hours of fun.
“Anyway, that’s what it is. I was really happy to be here today and play in front of you guys, thanks for the support.”
Fans packed the 12,500-seat stadium to watch Williams’ farewell and tournament organizers set up a first-ever outdoor viewing area for another 5,000 people.
Inside the stadium, the fans raised banners reading “Thank you Serena”, “We will miss you 23” or simply “The Queen”.
The farewell bid ended with Williams accepting a gift from the Toronto Maple Leafs from the NHL and the Toronto Raptors from the NBA.
Williams is expected to play at the Western and Southern Open in Cincinnati next, followed by the US Open which she has suggested would be her final tournament.
Meanwhile, Coco Gauff defeated Wimbledon champion Elena Rybakina 6-4, 6-7 (8), 7-6 (3) in a marathon match of two hours and 49 minutes on Wednesday to advance to the last 16.
Nick Kyrgios also advanced to the last 16 with an impressive 6-7 (2), 6-4, 6-2 victory over world No. 1 Daniil Medvedev.
CNN’s Ben Morse contributed to this report.
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