Jelena Jankovic ended her skid against Caroline Wozniacki on Tuesday, booking a quarter-final clash at Indian Wells against second-seeded Agnieszka Radwanska.
Jankovic, seeded seventh, defeated 10th-seeded Wozniacki 6-3, 6-1 in a battle of former world number ones.
In a rematch of the 2010 final in the California desert won by Jankovic, the seventh-seeded Serb showed no sign of the back trouble that required several visits from the trainer during her third-round victory over Magdalena Rybarikova on Sunday.
"Yesterday I was a little bit scared," Jankovic said of the pain that began when she wrenched her back on a point early in the match against Rybarikova.
"If I had to play yesterday, I probably wouldn't be able to go on court."
Since her 2010 triumph here, Jankovic had dropped five straight decisions to Denmark's Wozniacki.
And with golf-star fiance Rory McIlroy courtside, Wozniacki was quick to gain the upper hand in this one, breaking for a 3-1 lead in the first.
But Jankovic reeled off 10 straight games to take a firm grip on the match.
Serving to extend the opening set, Wozniacki couldn't put a first serve in play and was broken at love.
The Dane, who won the title in 2011 and was runner-up last year to Maria Sharapova, was unable to convert three break points in the fifth game of the second frame.
After Wozniacki finally held for 5-1 in the second, Jankovic wrapped up the win in just 64 minutes, returning to the quarter-finals here for the first time since her 2010 triumph.
"I lost to her the last I don't know how many times, but right now I'm playing some pretty good tennis. I went on court trying to wait for my chances," Jankovic said. "Against her, if you go for too much, you just make so many errors and beat yourself.
"It happened to me a lot of times in the past. So I just tried to play solid and aggressive at the same time, waited for the right shots, and then executed."
Radwanska reached the quarter-finals with a 7-5, 6-3 victory over France's Alize Cornet.
Cornet, who stunned world number one Serena Williams in the semi-finals at Dubai last month, rallied from a 4-1 deficit in the opening set, breaking Radwanska twice as she won four straight games to take a 5-4 lead.
But serving for the set, she wasted two set points, the second with a double-fault, and that was the only opening Radwanska needed to take the frame.
In the second set, it was Radwanska who gave up the first break, but Cornet couldn't maintain her advantage and Radwanska broke her twice to grab the win.
Chinese top seed Li Na was to take on Canadian Aleksandra Wozniak under the floodlights on Tuesday night for a quarter-final berth.
The winner of that match will face Slovakian Dominika Cibulkova -- who lost to Li in the final of the Australian Open in January.
Cibulkova defeated eighth-seeded Petra Kvitova 6-3, 6-2.
Italian qualifier Camila Giorgi, who shocked defending champion Sharapova in the third round, couldn't maintain her momentum, falling 6-2, 6-1 to compatriot Flavia Pennetta.
Sixth-seeded Romanian Simona Halep reached the last eight with a 6-2, 1-6, 6-4 victory over rising Canadian star Eugenie Bouchard.
Halep will face Australian qualifier Casey Dellacqua, who advanced on a walkover when American Lauren Davis withdrew with a stomach ailment.