BRISBANE, Australia (AP) — Serena Williams has a badly sprained left ankle, Roger Federer an aching back and Kim Clijsters a sore left hip.
Add in a limping — but "I'll be OK" — Andy Murray, Rafael Nadal playing with a sore left shoulder from last season and the warmup tournaments for the Australian Open are beginning to look like a star-studded sports injury clinic.
Williams' injury seems to be the most serious and could affect her chances of winning the singles title for the sixth time at Melbourne Park. She rolled it badly in the second round at the Brisbane International and pulled out of the tournament.
In her first tournament since losing the U.S. Open final in September, Williams was serving for the match against Bojana Jovanovski of Serbia when she twisted her ankle and fell to the court.
After receiving medical attention, she limped through the end of that game and the next to complete a straight-sets win. She later withdrew after medical scans "confirmed that I have a left ankle sprain (and) that I probably shouldn't play on."
On Saturday, Williams sounded optimistic in a brief message to her nearly 2.4 million Twitter followers.
"Team Williams on way to Melbourne.. I'm doing everything to heal up and winfromwithin," she tweeted.
Federer and defending Australian Open champion Clijsters withdrew from their tournaments on Friday. Federer, a four-time Australian Open singles champion, withdrew ahead of his scheduled Qatar Open semifinal against Jo-Wilfried Tsonga because of back muscle spasms. But said he expects to be fit for the first Grand Slam of the season when it begins on Jan. 16.
The 16-time Grand Slam singles champion said his back had not improved since beating Andreas Seppi in three sets on Thursday.
Clijsters was forced to retire from her semifinal match against Daniel Hantuchova at the Brisbane International. Clijsters won the opening set 7-6 (4) but surrendered a break at the start of the second set and needed treatment after the third game. She came back on court for one game before walking to the net and telling Hantuchova she couldn't continue after falling behind 3-1.
On Saturday, the WTA said a scan showed there was no tear but she had suffered a spasm in the muscle that helps control movement in the hip.
"Kim will be resting for a few days and getting intensive treatment, but the Australian Open should not be in danger," the WTA said, adding that Clijsters will have another scan next week.
Both Clijsters and Williams, the 2010 Australian Open champion, were playing their first tournaments in four months. Clijsters struggled with injuries last season and only played eight tournaments, including the win at the Australian Open that helped her return to the No. 1 ranking for one week.
She said her hip had started to go into spasm during the match and she withdrew to avoid a serious rupture.
"I felt my left hip was getting tighter and tighter to the point I couldn't move forward with my upper body," she said. "So it was the smartest choice to try and not let it get any worse, to be ready for Melbourne."
Players have complained in the past that the Australian Open is too early in the season, with most having limited tournament play after the offseason. The heat in the Australian summer is another issue and the predominance of hardcourt tournaments is often cited as contributing to injuries.
"Oh, it's definitely more demanding," Clijsters said of the hard courts, but "I think every surface has their advantages and disadvantages.
"It's just — our sport has evolved into such a strong sport where physically — I mean, it's so much more demanding on the body and how we play."
Clijsters said players were spending more time in the gym to build strength to cope with the increasing demands on their bodies and many traveled with a physical therapist.
"When I came on tour ... nobody was hardly ever in the gym besides warming up with a skipping rope or doing some shoulder exercises and now there's everybody — because it's necessary," she said. "The tennis that I play is physically so demanding on the body and then ... combine that on a hard court."
Murray dropped the opening sets of his first two matches at the Brisbane International as he overcame soreness and stiffness from the offseason. But a sleek-moving Murray appeared to back up his "I'll be OK" comment by beating young Australian hope Bernard Tomic in straight sets in the semifinals Saturday, less than 24 hours after he breezed through a quarterfinal against 2006 Australian Open finalist Marcos Baghdatis.
Nadal, who has struggled with a sore left shoulder, was beaten in straight sets by Gael Monfils in the Qatar Open semifinals on Friday. But he did not blame any injury problems for the loss.
There have been several other injury pullouts. Sixth-seeded Alex Bogomolov Jr. of Russia withdrew from Qatar with a right ankle injury. At Brisbane, Florian Mayer retired with a groin injury and Tommy Haas with a calf muscle injury.
Maria Sharapova withdrew before the Brisbane tournament with an injured ankle but has already arrived in Melbourne to begin training.
Venus Williams announced in mid-December that she was pulling out of the ASB Classic in Auckland, New Zealand, which was supposed to be her first competitive match since August. The 31-year-old Williams is still recovering from the immune system disease Sjogren's syndrome, which can cause fatigue and joint pain.
There has been no word on Venus' status for the Australian Open. Her sister's fitness for Melbourne likely will be in doubt until just before the tournament starts.
"I'm going to take a couple of days off — not too many — and see how I feel," Williams said after her withdrawal at Brisbane. "I'm still hopeful of playing the Australian Open."