Shanghai - Andy Roddick withdrew from the Masters Cup shortly before his match on Wednesday, citing an ankle injury he suffered during training the day before.

The American, who lost his opening match to Andy Murray, will be replaced in the Red group by Radek Stepanek.

The American dropped his bombshell a few hours before he was due to take to the court against Roger Federer.

Shanghai - Andy Roddick withdrew form the Masters Cup shortly before his match on Wednesday, with his place taken by Radek Stepanek.

Shanghai  - Novak Djokovic couldn't be more pleased after reversing his 2007 run of year-end bad luck by qualifying a year later for the semi-finals of the Masters Cup.

The world number three Serb, who cemented his place with a three-set victory Tuesday over Nikolay Davydenko, goes into his last red group match against Jo-Wilfried Tsonga relaxed and calm.

Shanghai - Juan Del Potro didn't allow his mind to stray to the upcoming Davis Cup final as he handed Frenchman Jo-Wilfried Tsonga a 7-6 (7-4), 7-6 (7-5) Gold group defeat at the Masters Cup on Tuesday.

The clash between the pair of 2008 breakthrough rookies at the season-ending championships gave the Argentine a 1-1 record and saddled Australian Open finalist Tsonga from France with two defeats from as many matches.

"I'm in the Masters Cup, I want to be alive until the finals, if I can," Del Potro said.

Shanghai - Juan Del Potro kept his hopes alive for an extended stay at the Masters Cup, winning a battle of first-time players 7-6 (7-4), 7-6 (7-5) over Jo-Wilfried Tsonga on Tuesday.

The Gold group clash between year-end rookies gave the Argentine a 1-1 record and saddled Australian Open finalist Tsonga from France with two defeats from as many matches.

"I'm in the Masters Cup, I want to be alive until the finals, if I can," he said.

London - A former doubles partner of John McEnroe has compared Brit Andy Murray to the American former bad boy of the game.