Melbourne, Jan 27 (DPA) Top seed Serena Williams saved the day from a looming family disaster, posting a comeback quarter-final win even as sister Venus lost at the Australian Open tennis Wednesday.

The invincible reputation of the seeded US sisters had taken a big hit when number six Venus was humbled by Li Na 2-6, 7-6(4), 7-5.

China’s Li made history by joining compatriot Jie Zheng in the semi-finals, making it the first time that two Chinese have done so in a Grand Slam. Li next plays former number one Justine Henin.

Serena also looked to be in desperate straits, down a set and 4-0 against Belarus seventh seed Azarenka. But the Belarusian let her momentum slip, with number one Williams scratching to 4-6, 6-7(4), 6-2 survival.

The top seed admitted that she had her mind on what looked to be an upcoming plane trip home before rallying.

“I’m surprised, I didn’t expect to win being down 0-4. I was thinking that if I went out in doubles, that I could catch a flight on Friday. But I’m just happy to still be here,” she said.

Against Azarenka, who beat her in the Miami final last spring, Serena came to the court without the loss of a set and with just 15 games lost. She ended her turnaround after two and a half hours as she bids for a fifth title in Melbourne.

Five-time Wimbledon champion Venus cracked under pressure against Li after serving early on for a comfortable straight-set victory, allowing the 16th seed to begin a grinding comeback.

Li broke Venus Williams four times in the third set as the American’s unforced error count raced past 50.

“This is the best day of my whole life,” said Li, who was two points from defeat at one stage and is to become the first Chinese ever to rank in the top 10 in Monday’s rankings.

“I lost the first set, but my coach tells me never to give up,” she said of Swede Thomas Hogstedt. “This is good for both of us and for China tennis.”

Venus was unable to make an impression once Li got her comeback going with the winner finishing with a pair of sizzling forehands.

“I felt really confident going into the match,” Venus Williams said. “Even in the third. I was leading.

“In tennis you have to close it out. It’s not like there’s a clock ticking and then suddenly it’s over,” she said. “You just have to close it out. I didn’t do that today.”

“She obviously started to play a lot better, she hits the ball so well. I give her a lot of credit for playing really well.”

She lost serve eight times, with 53 unforced errors and an 11th double-fault in the penultimate game as Li broke for the final time prior to serving it out on her third match point, a forehand winner down the line.

“In the second set I was feeling a little bit better,” Li said. “But was 5-3 down. Then I just tried to play more [getting the] ball back. I had chances and I was able to do it.”