MELBOURNE, Australia — Serena Williams saved some family pride Wednesday at the Australian Open.

After older sister Venus' loss to Li Na of China in the previous match on Rod Laver Arena, four-time champion Serena was down a set and 4-0 in the second before rebounding for a 4-6, 7-6 (4), 6-2 win over Victoria Azarenka of Belarus.

Top-seeded Roger Federer overcame an awkward start to win 13 straight games and beat Nikolay Davydenko 2-6, 6-3, 6-0, 7-5 to reach the semifinals for a 23rd straight Grand Slam.

Novak Djokovic, who beat Federer in the semifinals here two years ago en route to the title, was beaten by the man he defeated that year, Jo-Wilfried Tsonga of France, in a later quarterfinal.

Tsonga beat Djokovic 7-6 (8), 6-7 (5), 1-6, 6-3, 6-1 in a near four-hour match and will play Federer in a semifinal Friday. Djokovic appeared to be affected by breathing difficulties and stomach problems during part of the match and took a medical timeout trailing 2-0 in the fourth set.

Last year, Djokovic retired in the fourth set of his quarterfinal with Andy Roddick with a heat-related illness, but the weather conditions Wednesday night were cool and breezy.

"I think I was in good shape, maybe better than him," the 10th-seeded Tsonga said.

Andy Murray and Marin Cilic are already through to the semis and will play Thursday night.

Federer is impressed with his Grand Slam semifinal streak.

"It's incredible, looking back on how many years that is now, I'm able to deliver at Grand Slam play," Federer said. "For some reason I was just a bit worried I was not going to make it this time in the semis.

"Now obviously that it's safe again and I've been able to add one. Definitely one of the most incredible things I have in my resume."

Federer's victory snapped a 13-match Davydenko winning streak after the Russian won the season-ending ATP World Finals in November at London and his 20th career title in Doha earlier this month.

"I've played him many times before, and I know he goes through ... some rock-solid phases at times," Federer said. "I just tried to stay positive."

Venus Williams couldn't make it to an expected sister semifinal, losing in a mistake-filled match featuring in a combined 110 unforced errors against Li.

The result is that Serena will take on Li, who beat Venus 2-6, 7-6 (4), 7-5. Justine Henin, playing in her first Grand Slam tournament in two years after coming back from a two-year retirement, will play Zheng Jie in the other semifinal.

Serena Williams was far from confident after the first hour of the match, thinking of her sister's loss.

"It was obviously on my mind," Serena said of Venus' defeat. "I saw maybe one or two points, maybe three. I don't want to watch too much, I get too nervous watching. Obviously I was incredibly disappointed."

So she started off tentatively.

"I wasn't playing my best, especially in the first two sets," she said. "I was down the whole match from the first point. I wasn't surprised but I was definitely shocked."

Instead of wilting, she fought back from her big deficit in the second set with two service breaks of her own, easily won the tiebreaker and dominated the third.

Li and Zheng were the first Chinese pair to reach the quarterfinals at the same Grand Slam. Add semifinals now, and could the final be possible?

Serena Williams and Henin, with a combined 18 Grand Slam singles title between them (Serena 11, Henin 7) would seem to have the inside edge. But Li, who lost the first set and was twice down breaks in the second, says anything can happen.

"In China, we say if you have tough time and then you return back, maybe have good luck," Li said.

Venus Williams had more mistakes than luck against Li, who called the win the "best day of my life" and said she might celebrate with a beer Wednesday night.

"It's important to put the ball in the court," said Venus Williams, who served for the match in the second set. "I felt like sometimes I made some errors."

That was an understatement. The pair's unforced error count went over the 100 mark midway through the final set, which produced eight service breaks in the first 10 games.

"Unfortunately I let my errors creep in, and then I allowed her to dictate too much," Williams said. "But she played really well."

Azarenka wilted in her fourth-round match with Serena here last year, retiring in the second set with a virus after taking the first set.

This time, the 20-year-old Belarussian was undone by a trademark comeback by Williams, who is the only player to save match points on the way to three Grand Slam titles. She did it at Wimbledon last year and at the 2003 and 2005 Australian Opens.

Initially, Azarenka looked like she'd continue the Williams family woes. She broke Serena in the opening game and then, after fending off three break points, held her own opening serve in a game that lasted more than 15 minutes and went to deuce nine times.

It was mostly one-way until Williams started her comeback in the second — winning five straight games and then getting on top again at the end of the tiebreaker. She dominated the third set, converting both her breakpoint chances.

Li, who is forecast to go into the WTA's top 10 rankings after the tournament ends, was dominant in the third set when it counted against Venus Williams, who has five Wimbledon titles and two at the U.S. Open.

"I don't like losing at all," Williams said. "No one does. I put in a lot of hard work to come out here and get a win (I'm) not at all pleased."