Serena Williams continued her comfortable passage with victory in the third round of the Australian Open, but defending champion Victoria Azarenka was put to a serious test by an inspired American Jamie Hampton.
Williams eased past Japanese Ayumi Morita 6-1, 6-3, and looks on course to clinch her third straight Grand Slam title, after winning Wimbledon and the U.S. Open last year.
However, it was not so cut and dry for Azarenka, the player Williams is scheduled to meet in the semi-finals, with the world No. 1 having to overcome the feisty and powerful Hampton in three sets 6-4, 4-6, 6-2.
Azarenka did enough to take the first set with a single break, but Hampton came out all guns blazing in the second. The 23-year-old American's chances, however, looked bleak when she called for a medical timeout for a back problem.
"Going into the match I was fine," Hampton said. "About 4-2, 4-3, my back started hurting. I had back problems. Hurt my back last year at the French Open pretty badly.
"It's something I deal with day to day, and, yeah, it was hurting. Normally when my back starts hurting I start cramping."
Hampton, though, gritted her teeth and served out the second set, but looked in constant pain in the final set, with Azarenka having to pull out all the stops to clinch the decider.
"She played incredible," Azarenka said after the match. "She took a medical timeout but she rips winners all over the place and I was like, 'Can I have a back problem?' I'm feeling great, but I'm missing every shot."
Hampton revealed the back problem was an issue she has to deal with prior to every match.
"I probably shouldn't be telling you this, but I have two herniated disks in my lower back," she told reporters.
"It's tough. I mean, I play with those shorts, which don't look great, by the way, and then I have my back taped up pretty good before every match.
"I just try to manage it on the court and slow down, take my time. When I got low it was really hurting, and there's not really much you can do. I try my best, but...
"I'm sure in a few days it will be a lot better. Take some medication, see the doctor and physios, get as much treatment as I can, go home and see my physio, make my core and back as strong as possible."
Elsewhere, Maria Kirilenko, seeded 14, got the better of No. 20 seed Yanina Wickmayer 7-6 (4), 6-4, while Russian veteran Svetlana Kuznetsova fought past Carla Suarez Navarro of Spain 6-2, 4-6, 6-3.
