Publications
Partners
Clijsters, who rolled her ankle midway through the first set and needed medical treatment, came back from 6-2 down in a second-set tiebreak to defeat shell-shocked Li 4-6, 7-6 (8/6), 6-4 in 2hrs 23mins.
Earlier third seed Azarenka defeated Czech Iveta Benesova 6-2, 6-2 and Radwanska, the eighth seed, smashed Germany's Julia Goerges 6-1, 6-1 to set up a quarter-final clash.
Clijsters staged a magnificent turnaround after looking down and out as she hobbled to her chair at 3-3 in the first set when she hurt her ankle during a baseline rally.
Her sheer determination enthralled the big crowd in Rod Laver Arena, who swung their support behind the 28-year-old, making her last tournament appearance in Australia before retiring at the end of 2012.
"A couple of times it went through my mind (to retire from the match), but I didn't want to quit at my last time at the Australian Open," she said.
Clijsters managed to hold her serve after the injury, coming back from a break point down to save the game, but Li then broke Clijsters' next service game and held her own to take the first set in 43 minutes.
After going down an early break in the second Clijsters began moving better and she broke to get the set back on level terms and into a tiebreak.
Li opened a 6-2 lead, only for Clijsters to win six points in a row to level the match. She then raced to a 4-0 lead in the third set as Li buckled.
The Belgian served for the match once at 5-2 but was broken, then had a second chance at 5-4 and this time made no mistake, claiming victory when a Li backhand hit the net on her second match point.
Azarenka has dropped only 12 games in her run to the quarter-finals and she was quickly into her stride against Benesova, breaking twice in the first set.
She maintained her firm grip on the contest in the second set, again breaking twice to wrap up the match in 1hr 17mins.
Azarenka, who is in contention to secure the number one ranking after the Australian Open, said she felt full of confidence after her win in Sydney earlier this month, which means she is still unbeaten this year.
"Of course I'd be a liar if I said I don't care about it but it's a little bit in the back of my mind," she said of her chances of reaching the top spot.
Radwanska, 22, needed just 54 minutes to reach the quarter-finals for the second year in a row. She made just three unforced errors in the match as opposed to 27 from Goerges.
Azarenka and Radwanska met in the semi-finals in Sydney earlier this month, when the Belarusian prevailed in three sets on her way to the title.
