Wozniacki will take on good friend Radwanska in the semi finals
Caroline Wozniacki held off a battling Zheng Jie to reach the last four of the BNP Paribas Open in Indian Wells.
The Danish second seed resisted a sizzling baseline display from the Chinese player to earn a hard-fought 6-4 4-6 6-1 victory.
"It was really tough," said Wozniacki. "She got a lot of balls back that I thought I had won already."
Wozniacki will now play Agnieszka Radwanska in the semis after her 6-4 6-3 win over Elena Dementieva.
Radwanska, who has yet to drop a set at Indian Wells this year, broke her opponent twice in each set to win the match in one hour, 31 minutes.
"I'm very happy I am in this condition, always playing two sets," said Radwanska after sealing victory when Dementieva hit a backhand service return long.
"It's always better to win in two sets but it's hard, especially here.
"It's tough, especially against Dementieva, who is also very tough to play against. I'm just happy about my performance this week."
Dementieva admitted that her tally of 54 unforced errors did not help her cause.
"I didn't play the way I should be to beat her," said the fourth seeded Russian, who lost in the final at Indian Wells to Maria Sharapova in 2006.
"I was playing her game, the way she feels pretty comfortable with the long rallies.
"I feel I was not aggressive with my footwork, was not aggressive with my shots today, so just way too many mistakes from me."
Wozniacki was pushed all the way in her quarter-final clash, which lasted two hours, 18 minutes.
She fended off four break points in the final set while claiming three breaks of her own as she secured a first win in three matches against Zheng.
Wozniacki said of her good friend Radwanska: "She's a good player. She's getting a lot of balls back. She's thinking. She's smart on the court. But she's a good friend.
"On I think we're just going to relax and have fun."