ADELAIDE (AFP) -- Both top seeds at the ATP-WTA Adelaide International suffered quarterfinal shocks on Thursday, Jan. 11, with Elena Rybakina and Tommy Paul exiting in straight sets.

World number three Rybakina, the 2022 Wimbledon champion and last year's Australian Open finalist, was stunned 6-3, 6-3 by Ekaterina Alexandrova, who led 4-0 in both sets.

American Paul crashed 6-1, 6-4 to Briton Jack Draper.

Russian-born Kazakh Rybakina, who won the Brisbane International last weekend, fell two breaks behind in the opening set and did not win a game until 24 minutes into the match.

She rallied in vain, losing the first set and trailing 5-0 in the second, putting up a late fight before slumping out to her 21st-ranked Russian opponent.

"I didn't have many expectations," Alexandrova said. "I tried to play every point. My serve (six aces) was a big help today."

Alexandrova will now meet sixth seed Jelena Ostapenko, who survived a wobble in the first set but regained concentration to ease past Ukrainian Marta Kostyuk 7-5, 6-3.

"It was a tough match of course," Ostapenko said.

"There have been times when I've needed to step into the point and put more pressure on the opponent. I need to go for my shots, even if I miss."

One quarterfinal was determined without a ball struck when Germany's Laura Siegemund pulled out of her match with Russia's Daria Kasatkina injured.

Kasatkina will play American second seed Jessica Pegula, who struggled to get past veteran qualifier Anastasia Pavyluchenkova 6-7 (1/7), 7-5, 6-4.

"She was hitting so hard, taking the ball early," world number five Pegula said. "I don't know how I stayed in it."

American Paul joined men's second seed Nicolas Jarry of Chile on the sidelines at the last event prior to the Australian Open.

Jarry lost 6-4, 7-5 to Czech Jiri Lehecka.

The 62nd-ranked Draper dominated the match against Paul from the start, running away with the first set and battling in the second to set up a semifinal against Alexander Bublik.

Russia's Bublik ousted Italian fourth seed Lorenzo Musetti 6-3, 6-7 (4/7), 7-5.

Third seed Sebastian Korda powered into the semifinals for a second straight year, but needed five match points to set up a last four clash with seventh seed Lehecka.

The American, son of 1998 Australian Open winner Petr Korda, finished runner-up at Memorial Drive in 2023, losing to Novak Djokovic.

He defeated Christopher O'Connell 6-4, 6-4 to keep his dream alive of going one better this year.

"I didn't play badly on the match points, but he really raised his level," said Korda, an Australian Open quarterfinalist last season.

At the WTA Hobart International, Belgian top seed Elise Mertens stayed on track with a 7-5, 6-0 win over the Netherlands' Arantxa Rus.

She will face Daria Saville for a place in the final after the Australian fought past China's Zhu Lin in three sets.