MELBOURNE, Australia - Once her most successful major, the Australian Open has become Serena Williams' snake bit-Slam.
No. 1 Williams, a five-time champion, saw her tournament go up in smoke Sunday when she lost to No. 14 seed Ana Ivanovic of Serbia 4-6, 6-3, 6-3 in the fourth round.
Williams didn't look herself and later confirmed she was hampered by a back injury she picked up in practice between the second and third rounds.
"I almost pulled out," a disappointed Williams said of her third-round match against Daniela Hantuchova on Friday. "I'm such a competitor. I mean, I probably should have."
The loss snapped the American's 25-match winning streak going back to August before she won her fifth U.S. Open.
Williams also had been 51-1 in Melbourne when winning the first set, her only loss to fellow American Sloane Stephens in last year's quarterfinals when she was hobbled by an ankle injury.
But full credit to Ivanovic.
The former No. 1 attacked returns, stuck to her strategy and played some of the boldest tennis since she won her sole major at the 2008 French Open.
Ivanovic, who had not won a set in four previous meetings with Williams, didn't falter either when she let a first-set lead slip.
"I was very competitive till the last moment, and I'm just very thrilled, obviously," said Ivanovic, 26, who lost to Maria Sharapova in the 2008 Australian Open final.
Aces aside - Williams led that category 13-1 - Ivanovic was the aggressor with 33 winners to Williams' 22, including 20 on her forehand side.
"I feel like Ana deserves all the credit," said Williams. "I feel she played unbelievable today. I think she went for her shots. It's not like I gave her the match."
Williams captured five of 11 Australian Opens she entered through 2010 - more than any other of the other three majors at the time - but for the third year running exited the tournament before the semifinals at least partly due to a compromising injury.
In 2012, she injured the same ankle as last year in a warm-up tournament and fell in the round-of-16 to Russia's Ekaterina Makarova.
She dismissed the notion her fortunes had changed, emphasizing that she was champion in 2003, 2005, 2007, and 2009-10.
"I think I have done pretty well here," said Williams, now also a five-time champion in New York and at Wimbledon. "I feel like I'll win it again."
Williams' coach, Patrick Mouratoglou, said Williams hurt her back in practice before her 6-3, 6-3 defeat of Slovakia's Hantuchova and considered pulling out 30 minutes beforehand.
"It was much, much worse the round before," he said of Williams' back. "She couldn't play at all."
Two days ago, Williams and her sister, Venus Williams, withdrew from the doubles competition at the Australian Open before their first-round match, citing a lower left leg injury to Venus.
Mouratoglou didn't blame Sunday's loss entirely on her back but said Ivanovic outplayed Williams.
"She was better everywhere today," he said.
Williams said she didn't know the exact nature of the injury and had been taking "the strongest meds I can take" to manage it the past few days. She said it was not "life-threatening" and would likely be better after a couple days' rest.
"Unfortunately I don't have that in a Grand Slam," she said.
While Serena was not her best, Ivanovic impressed.
Since her ranking peak five years ago, Ivanovic has wrestled with on court demons and rarely been a factor in major championships. She has cycled through coaches, tinkered with her racket, and talked to sports psychologists.
She admitted this week that she had made some poor choices, but with an all-Serbian team around her now, including coach Nemanja Kontic, Ivanovic is starting to hit her stride.
"Now looking back at it, I would have done few things differently," said Ivanovic Sunday, who is now 9-0 in 2014 after winning her opening-season tournament at Auckland. "I maybe took a few different or good or wrong advices. But it's just a road, and we all have to pass through certain parts, and mature in the way."
Last year, Williams won a career highs in titles (11) and matches (78), including her 16th and 17th majors at Roland Garros and the U.S. Open.
After her dominant season, some speculated that despite her age she could possibly win all four majors in a single year - a true Grand Slam.
"I have given up on that a long time ago," Williams smiled, vowing to get back to work "as if I'm ranked 1,000 in the world."
But after another physical problem Down Under, health may be her biggest obstacle as she tries to reel in the likes of Chris Evert and Martina Navratilova, who are next up the ladder of Grand Slam champions with 18 major titles each.
"I feel like I know for a fact I can play so much better than what I did today, so with that, knowing that, I'm not disappointed or anything," Williams said while trying to strike an upbeat note. "I just know that I can play ten times better than what I did today."
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