Serena Williams on Friday crashed out of the Lexington Top Seed Open in Kentucky, surprisingly beaten by 116th ranked American Shelby Rogers in the quarter-finals.
Williams – the top seed and 23-time grand slam champion – was ousted 1-6 6-4 7-6 (7-5) by Rogers.
Stepping up her preparation ahead of this month’s US Open in New York, Williams overcame sister Venus in the last 16 on Thursday but the 38-year-old star was unable to continue her run at the WTA International event.
Rogers – in her first meeting against Serena Williams – rallied from a set down in the all-American affair to earn a semi-final showdown with Jil Teichmann, who accounted for Cici Bellis 6-2 6-4.
“It was important for me going onto the court thinking I could win that match, and knowing I could take care of my service games,” Rogers said.
“Because [Williams] has probably the best serve of all time, and when she wants to, she can win a point on her serve.”
Teenage sensation Coco Gauff, meanwhile, fought back from a set and a break down to top eighth seed Ons Jabeur 4-6 6-4 6-1.
Gauff trailed 6-4 4-2 but the 16-year-old American completed a thrilling comeback to reach her second WTA semi-final.
Awaiting Gauff in the semi-final is countrywoman Jennifer Brady, who eased past Marie Bouzkova 6-1 6-2.