Williams was beaten by Shelby Rogers 1-6 6-4 7-6 (7-5), as the world No.116 picked up only her third career victory over a top-10 opponent.

Rogers, who took six of the last eight points after trailing 3-1 in the tiebreaker, also reached her first WTA semi-final since 2016.

Former world No. 1 Williams, the owner of 23 grand slam singles titles, hadn't bowed out against someone so low in the rankings since No. 111 Virginie Razzano stunned her at the 2012 French Open.

Shortly after that, Williams teamed up with coach Patrick Mouratoglou who still works with her.

This was the third consecutive three-setter for Williams at the hard-court Top Seed Open.

She dropped the opening set of each of the others before coming back to beat Bernarda Pera in the first round, then older sister Venus in the second.

"I could play a lot better, I think that's the main thing I can take from this match," Williams said.

"I made it difficult on myself by making a plethora of unforced errors."

With social-distancing rules in place, the players didn't meet at the net for the customary post-match handshake. As they headed to their sideline seats, Williams smiled. Rogers simply sat down and quickly shook a fist.

"It's every kid's dream when they are growing up watching her play and to be able to do something like that," said Rogers, who has yet to get used to the unfamiliar surroundings as the event is being played without any fans in attendance due to the COVID-19 pandemic.

"Weird circumstances. Weird setting. But a win is a win. I know we're all just happy to be playing."

Rogers will now face Jil Teichmann in the semi-finals on Saturday. Teichmann needed seven match points to reach the first hard-court semi-final of her career with a 6-2 6-4 victory over Cici Bellis.

The semi-final on the other side of the draw will be Jennifer Brady against 16-year-old Coco Gauff, who battled back to defeat Tunisian No.8 seed Ons Jabeur 4-6 6-4 6-1.

Brady advanced by beating Marie Bouzkova 6-1 6-2.

Australian Associated Press