MIAMI • Fears that Serena Williams' best days are behind her grew on Monday when tennis' women's world No. 1 suffered a surprise fourth-round defeat at the hands of Svetlana Kuznetsova at the Miami Open.

The American, beaten in the Australian Open final by Angelique Kerber in January and by Victoria Azarenka in the BNP Paribas Open final at Indian Wells this month, looked lacklustre for much of her 6-7 (3-7), 6-1, 6-2 defeat by Kuznetsova, the 30-year-old Russian who won this title 10 years ago.

Williams has won the tournament for the past three years but made 55 unforced errors and served nine double faults in a comprehensive defeat.

At times she barely seemed to care, although there may have been some sort of physical problem.

By way of an explanation, the best Williams could offer came when she said: "She just won more games than me. I did the best I could but I can't win every match.

"Physically I was fine, but I guess I just didn't move today. They come out against me and play their best and I have to be 300 per cent every time."

Williams was bidding for her ninth title in the event and her fourth in a row. But, after a gruelling first set that lasted nearly an hour, the No. 1 seed faded on a sweltering afternoon.

This is the first time she has not reached the Key Biscayne quarter-finals since 2000, when she lost in the fourth round to Jennifer Capriati.

The 34-year-old has not won a tournament since earning her 69th title at Cincinnati in August - a run of four events that included the US Open (semi-final), Indian Wells (final) and Australian Open (final).

It was a day of dramatic upsets at Crandon Park, as third-seeded world No. 2 Agnieszka Radwanska was beaten by 19th-seeded Swiss Timea Bacsinszky 2-6, 6-4 6-2.

Later, fourth-seeded Spaniard Garbine Muguruza was beaten 7-6 (8-6), 7-6 (6-4) by 13th seed Belarusian Victoria Azarenka, while second seed Angelique Kerber narrowly avoided being another victim as she squeaked past Timea Babos 6-2, 3-6, 6-4.

In the men's tournament, world No. 2 Andy Murray was knocked out in the third round by Grigor Dimitrov, who came from a set down to triumph 6-7 (1-7), 6-4, 6-3.

Going down to the man who ruined his Wimbledon title defence two years ago was not a disgrace but the manner of the defeat, with Murray hitting 55 unforced errors and losing the last five games of the match, three on his own serve, will certainly be cause for concern in the Scot's camp.

When Dimitrov won the second set, Murray took his frustration out on his racket, which earned him a violation from the umpire.

"It's very disappointing, that's for sure," said Murray, who also lost in his second match in Indian Wells and has only two wins on the ATP World Tour since reaching the Australian Open final in January.

He must now regroup in time for the European clay-court season that begins for him in Monte Carlo in a fortnight.

"Normally I feel very much at home at this event and have a decent run. I had opportunities in this match and played some decent tennis at times. But, after winning the first set, I just let things go. Even then I was 3-1 up in the final set but then the unforced errors really crept in and I lost five games in a row," said Murray.

His coach, Amelie Mauresmo, did not sit with the rest of his support team and wife Kim. But he denied any rift in the camp and said: "It's just about trying to find a different way to focus on the court. If there had been fallout with Amelie, then she would not be here at all."

THE TIMES, LONDON,

AGENCE FRANCE-PRESSE, REUTERS

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