Two-time defending U.S. Open champion Kim Clijsters withdrew from the tournament Friday because of a stomach muscle injury.

Clijsters, who missed Wimbledon with an ankle injury, pulled out of a tournament in Toronto this month with a muscle strain on the left side of her stomach. In a statement Friday, she said "two weeks of rehab is not enough to heal this injury."

Roberto Mancini admits he is now spoilt for choice as he mulls over the prospect of introducing Sergio Aguero into a four-man Manchester City strike force against Bolton Wanderers.

Aguero made an instant impact on his Manchester city debut, scoring twice after coming on as a second-half substitute in the 4-0 opening-game win over Swansea.

Novak Djokovic survived a scare before easing through to the semis, but Rafael Nadal and Roger Federer's U.S. Open preparations hit a snag at the ATP Cincinnati Masters on Friday.

World No. 1 Djokovic outlasted Frenchman Gael Monfils to win 3-6, 6-4, 6-3 in a two and a half hour evening match.

The start of the Spanish league season will be delayed by a strike after Spanish league officials and player representatives failed on a last-minute deal.

The Association of Spanish Football Players said the strike will go ahead after talks failed Friday for improved salary guarantees in a new collective bargaining agreement.

Arsenal may have not lost at home to Liverpool since the turn of the Millennium but the Gunners are already looking unusually vulnerable just two games into the new season.

The departure of Cesc Fabregas and the impending sale of Samir Nasri has left manager Arsene Wenger short of two of the top performers from last term ahead of Saturday's lunchtime kick off at the Emirates Stadium.

Andre Villas-Boas faces an early goalkeeping dilemma at Chelsea after Petr Cech was ruled out for up to four weeks with a knee ligament problem ahead of the visit of West Bromwich Albion.

Cech was injured when he fell under the weight of a colleague during training this week and Villas-Boas must now decide whether Hilario or Ross Turnbull should replace the Czech Republic international.

Twenty years on from his sensational debut as a virtually unknown Formula One driver Michael Schumacher has this week insisted that he will race with Mercedes in 2012 despite widespread rumors that he is set to quit.

The seven-times drivers world champion, now 42, has struggled through a disappointing season so far, but broke off from the final days of his summer holidays to stress that he has no plans to walk away - and no knowledge that he is about to be released.

McLaren team chief Martin Whitmarsh sounded the first fighting notes ahead of Formula One's resumption of racing hostilities next week by claiming both Lewis Hamilton and Jenson Button are still in with a chance of winning the drivers' world title.

As the F1 teams began to return to work after their summer holidays, an upbeat Whitmarsh said the task facing his men was tough, "but not impossible."

Rafael Nadal wanted to play a lot of tennis at the Western & Southern Open, though maybe not all in one day.

Nadal survived a three-set, three-tiebreaker match against fellow Spaniard Fernando Verdasco on Thursday, advancing to the quarterfinals with a 7-6 (5), 6-7 (4), 7-6 (9) victory that kept him on court for 3 hours, 38 minutes. Then, he played a doubles match that went an hour and 10 minutes, followed by interviews.

Spain reacted with outrage Thursday after Barcelona's 3-2 Super Cup win over Real Madrid descended into violent scenes with defeated coach Jose Mourinho jabbing a rival in the eye.

Television images and photos on the front pages Thursday showed Mourinho poking his finger into the eye of Barcelona coach Pep Guardiola's assistant Tito Vilanova as players brawled on the field.