(CNN) -- Former world number ones Justine Henin and Kim Clijsters both survived scares before booking their spots in the semifinals of the Brisbane International event.
Henin, playing her first tournament since retiring from the sport in May 2008, looked on track for an easy victory after breezing through the opening set 6-2 against seventh seed Melinda Czink.
But the Hungarian, who is ranked 37th in the world, hit back to claim the second. The third set went the distance, with Czink fighting back from a break down before saving two match points at 4-5 and then forcing a tie-break.
But Henin's class and experience prevailed as she closed out the match 6-2 3-6 7-6 in two hours and 20 minutes.
The Belgian will now play third seed Ana Ivanovic in the semis after she defeated Russian Anastasia Pavlyuchenkova 6-2 7-6.
The Serb was in control from the outset, breaking her opponent twice on her way to an easy first set.
She carried that momentum into the second set, winning the first four games before Pavlyuchenkova mounted a comeback to force a tie-break.
The Russian raced out to a 4-1 lead in the breaker, but the world number 21 was not to be denied as she saved a set-point before closing out the match in just under an hour and a half.
Clijsters, meanwhile, was also made to work hard in her quarterfinal but eventually edged a rollercoaster clash with Lucie Safarova 6-1 0-6 6-4 at the Pat Rafter Arena.
The Belgian world number 18 broke her opponent twice en route the first set, but five double faults in the second helped Safarova get back on level terms.
The Czech could not maintain that sort of form and conceded an early break in the deciding set, but still made Clijsters work hard for her win.
Clijsters will next face German Andrea Petkovic, who secured her last-four spot with an upset 6-4 6-2 victory over fourth seed Daniela Hantuchova of Slovakia.
In the men's event, Czech second seed Radek Stepanek booked his last four place with a 7-6 6-1 win over American Wayne Odesnik.
He was joined in the last four by third-seeded Frenchman Gael Monfils, who receovered to beat American James Blake 3-6 6-3 6-4.
Roger Federer and Rafael Nadal remain on course to meet in the final of the Qatar Open after both claimed quarterfinal wins on Thursday.
Top seed Federer was taken all the way by Latvian Ernests Gulbis before going through 6-2 4-6 6-4, while Nadal had a simpler task to overcome Belgian Steve Darcis -- who retired while trailing 6-1 2-0.
Elsewhere, Israel's Shahar Peer defied noisy protests for a third straight day to make the semifinals of the Auckland Classic.
Peer was joined by third seed Yanina Wickmayer of Belgium, and Italian duo Francesca Schiavone and top seed Flavia Pennetta.
Police arrested five protesters from a group of around 20 outside the Auckland tennis complex as they chanted protests against Israel's Middle East policies.
But the 22-year-old shut out the distraction to triumph 6-0 3-6 6-1 in a see-saw match against Russia's Maria Kirilenko -- securing a last four place against Wickmayer.
Meanwhile, Spain advanced to the Hopman Cup final with a 3-0 win over Australia in their Group A tie in Perth.
The host nation needed to win all three rubbers in straight sets to snatch a final spot off the unbeaten Spanish pairing of Maria Jose Martinez Sanchez and Tommy Robredo.
But it took the in-form Martinez Sanchez just 41 minutes to snuff out Australian hopes, securing a fourth final appearance for Spain when she took the first set off Samantha Stosur.