SHANGHAI - World number one Roger Federer suffered a shock defeat to Fernando Gonzalez to put his Masters Cup defence in doubt on Monday.

The Swiss triple champion raced to a one-set lead but then lost a second-set tie-breaker by a mile before being edged out by the gutsy Chilean 3-6, 7-6 (7/1), 7-5 in front of a disbelieving crowd at Qi Zhong Stadium.

Roger Federer of Switzerland waves to the crowd as he leaves the court after losing his match to Fernando Gonzalez of Chile at the 2007 Tennis Masters Cup Shanghai. Gonzalez upset Federer 3-6, 7-6 (7/1), 7-5. [Agencies] It was a disastrous start from the 12-time Grand Slam winner, who had never lost a round-robin match at the season finale and enjoyed a 10-0 record against the seventh-ranked Chilean.

Federer, whose last match was a quarter-final loss to David Nalbandian at the Paris Masters, also suffered his first back-to-back defeats since 2003.

"It's tough because I thought I played pretty good," said the rueful Swiss.

"In some ways I have regrets and in some ways I don't, because I thought it was ridiculous the kind of shots he was coming up with.

"You have to give him credit for that. I hadn't been broken all the way through until the very end. He lost his serve but then he broke and held his serve, so that's that."

Federer started in typically ruthless fashion, breaking Gonzalez in his first game before wrapping up the first set in just 29 minutes.

However Gonzalez stalled the charge, taking the second set to a tie-breaker where Federer suffered an uncharacteristic implosion, fluffing an overhead and playing a panicky lob.

In the deciding set, Federer staved off break points in the third and fifth games but was broken for the first time for 6-5 as Gonzalez hammered ground strokes before finishing with a deft volley.

Gonzalez, who had saved five break points of his own, raced to 40-0 in the next game and celebrated a famous victory as Federer hooked a forehand wide.

"Nobody beats me 11 times in a row!" said the jubilant Chilean.

"Of course he was the favourite. I had a lot of motivation, I was really excited when I went to the court.

"I think he played the first five games like a real number one. But after that he went down a little bit and my level went up. I think the key to the match was my serve and not being scared to go for my shots."

The South American's heroics add unexpected spice to the Masters Cup, where Federer was the overwhelming favourite for his fourth title.

The 26-year-old Federer won the Masters in 2003, 2004 and 2006, falling to Lleyton Hewitt in the 2002 semis and losing a marathon final to Nalbandian in 2005.

Gonzalez, 27, is making his second appearance at the tournament after playing as an alternate in 2005, when he failed to reach the knock-outs.

In Red Group's earlier match, troubled Russian Nikolay Davydenko's horror season continued when he was hammered by racquet-breaking Andy Roddick.

Davydenko, the subject of an ATP betting probe, rallied from a set down to win the second, prompting the angry American to smash his racquet on the floor.

But the Russian collapsed in the decider, losing 6-3, 4-6, 6-2 in two hours and two minutes.

It was an impressive performance from the fifth-ranked Roddick, who has been labouring with foot and knee problems and shrugged off the racquet incident.

"I've always been pretty expressive and emotional on the court," he said.

"Sometimes it helps, sometimes not so much."

The result is further bad news for Davydenko, who has been questioned along with his wife and brother over a match he played in Poland in August.

Gambling website Betfair refused to pay out after unusually large sums were wagered on his opponent, 74th-ranked Argentine Martin Vassallo Arguello, who lost the first set but was handed the match when Davydenko retired injured.

The 26-year-old was then fined for not trying at St. Petersburg and warned by the umpire for again sending down multiple double faults against Marcos Baghdatis in Paris. He later blamed an elbow injury.

SHANGHAI - World number one Roger Federer suffered a shock defeat to Fernando Gonzalez to put his Masters Cup defence in doubt on Monday.

The Swiss triple champion raced to a one-set lead but then lost a second-set tie-breaker by a mile before being edged out by the gutsy Chilean 3-6, 7-6 (7/1), 7-5 in front of a disbelieving crowd at Qi Zhong Stadium.

Roger Federer of Switzerland waves to the crowd as he leaves the court after losing his match to Fernando Gonzalez of Chile at the 2007 Tennis Masters Cup Shanghai. Gonzalez upset Federer 3-6, 7-6 (7/1), 7-5. [Agencies] It was a disastrous start from the 12-time Grand Slam winner, who had never lost a round-robin match at the season finale and enjoyed a 10-0 record against the seventh-ranked Chilean.

Federer, whose last match was a quarter-final loss to David Nalbandian at the Paris Masters, also suffered his first back-to-back defeats since 2003.

"It's tough because I thought I played pretty good," said the rueful Swiss.

"In some ways I have regrets and in some ways I don't, because I thought it was ridiculous the kind of shots he was coming up with.

"You have to give him credit for that. I hadn't been broken all the way through until the very end. He lost his serve but then he broke and held his serve, so that's that."

Federer started in typically ruthless fashion, breaking Gonzalez in his first game before wrapping up the first set in just 29 minutes.

However Gonzalez stalled the charge, taking the second set to a tie-breaker where Federer suffered an uncharacteristic implosion, fluffing an overhead and playing a panicky lob.

In the deciding set, Federer staved off break points in the third and fifth games but was broken for the first time for 6-5 as Gonzalez hammered ground strokes before finishing with a deft volley.

Gonzalez, who had saved five break points of his own, raced to 40-0 in the next game and celebrated a famous victory as Federer hooked a forehand wide.

"Nobody beats me 11 times in a row!" said the jubilant Chilean.

"Of course he was the favourite. I had a lot of motivation, I was really excited when I went to the court.

"I think he played the first five games like a real number one. But after that he went down a little bit and my level went up. I think the key to the match was my serve and not being scared to go for my shots."

The South American's heroics add unexpected spice to the Masters Cup, where Federer was the overwhelming favourite for his fourth title.

The 26-year-old Federer won the Masters in 2003, 2004 and 2006, falling to Lleyton Hewitt in the 2002 semis and losing a marathon final to Nalbandian in 2005.

Gonzalez, 27, is making his second appearance at the tournament after playing as an alternate in 2005, when he failed to reach the knock-outs.

In Red Group's earlier match, troubled Russian Nikolay Davydenko's horror season continued when he was hammered by racquet-breaking Andy Roddick.

Davydenko, the subject of an ATP betting probe, rallied from a set down to win the second, prompting the angry American to smash his racquet on the floor.

But the Russian collapsed in the decider, losing 6-3, 4-6, 6-2 in two hours and two minutes.

It was an impressive performance from the fifth-ranked Roddick, who has been labouring with foot and knee problems and shrugged off the racquet incident.

"I've always been pretty expressive and emotional on the court," he said.

"Sometimes it helps, sometimes not so much."

The result is further bad news for Davydenko, who has been questioned along with his wife and brother over a match he played in Poland in August.

Gambling website Betfair refused to pay out after unusually large sums were wagered on his opponent, 74th-ranked Argentine Martin Vassallo Arguello, who lost the first set but was handed the match when Davydenko retired injured.

The 26-year-old was then fined for not trying at St. Petersburg and warned by the umpire for again sending down multiple double faults against Marcos Baghdatis in Paris. He later blamed an elbow injury.