By Nick Mulvenney
MELBOURNE (Reuters) - An inspired Ana Ivanovic blew the race for the Australian Open women's title wide open with a stunning upset of overwhelming favorite Serena Williams in the fourth round on Sunday.
The 14th ranked Serb played the match of her life to come from a set down and secure the biggest shock of the tournament so far with a 4-6 6-3 6-3 victory over the world number one.
Fourth seed Li Na and Italy's Flavia Pennetta, who both won fourth round matches earlier on Sunday, will have considerably more to play for in their quarter-final now the 17-times grand slam champion has been removed from their path.
Ivanovic, who will meet Casey Dellacqua or Eugenie Bouchard in her quarter-final, said she held nothing back against the top seeded American.
"It's amazing, when I came onto court I was just hoping to play as well as I could," she said. "I just went out there swinging at the ball and I did it really well."
Williams admitted to not feeling her best but offered no excuses.
That was until she realized coach Patrick Mouratoglou had told reporters about a back injury she sustained before her third round match.
"So he's the one that's snitching?" she said to laughter.
"I don't want to blame anything. I feel like Ana deserves all the credit. I feel she played unbelievable today. I think she went for her shots.
"It's not like I gave her the match. I tried to fight the best I could today."
Defending men's champion Novak Djokovic was next up on Rod Laver Arena, looking to avoid a similar upset at the hands of his friend Fabio Fognini.
'I ACTUALLY BELIEVED'
Williams was riding high on a winning streak of 25 matches going back to the start of last year's U.S. Open and had never even lost a set to Ivanovic in four previous meetings.
When Williams took the first set on Sunday it looked like the 32-year-old, who had lost just once in Melbourne in 52 matches after taking a 1-0 lead, would continue her march towards a sixth Australian Open title.
She looked a little lethargic in the opening stanza but has so often been able to count on her physicality and superior mental strength through such encounters without needing to be at her best.
Ivanovic won the French Open in 2008 but has done precious little in her sport's four majors since then and looked destined to become the latest in a string of former world number ones who failed to present a sustained threat to the American's dominance.
In the second set, though, the 26-year-old started to take the game to Williams, attacking her serve with success very few have managed and dictating the back court with her forehand.
Her tally of 20 forehand winners to two for Williams told its own tale but, most importantly, once ahead in the deciding set Ivanovic kept her head to keep Williams at bay before serving out to love for the match.
"I actually believed," said Ivanovic, who last reached the quarter-finals of a grand slam in 2012 at Flushing Meadows.
"I had some confidence coming into today's match. I really did certain things extremely well and I kept her under pressure I felt throughout the whole match.
"I just stayed in the moment physically. I didn't think much about the occasion and who I was playing, because it can get overwhelming."
China's Li earlier gave Ekaterina Makarova not so much as a sniff of an upset as she set up meeting with Pennetta by demolishing the Russian 6-2 6-0 in just under an hour.
The former French Open champion, who reached the final here last year and in 2011, briskly saved two break points in the first set, another couple at 3-0 up in the second and sealed the win with a backhand volley at the net to serve out to love.
Pennetta's journey to her first Australian Open quarter-final was a bit more complicated and she took 53 minutes longer than the Chinese to beat ninth seeded German Angelique Kerber 6-1 4-6 7-5.
Li had her own particular reason for being delighted to face the Italian.
"She's one day older than me, so for once I don't have to play a younger player," beamed the 31-year-old.
(Editing by Peter Rutherford)