Serena Williams crashed out of the Top Seed Open, the former world number one surprisingly beaten by 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 fellow American Rogers in Lexington on Friday.

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 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 final four is countrywoman Jennifer Brady, who eased past Marie Bouzkova 6-1 6-2.