With three weeks remaining in the regular ATP season, Croatian Marin Cilic, second-seeded Czech Radek Stepanek and French showman Gael Monfils, the number three, are all off the pace for the eight-man World Tour Final in London from November 22.

But the mathematics give decent chances even to the late runners, with a total of 1 750 ranking points in play over the next 21 days through the final of the Paris Masters on November 15.

Cilic, winner of two titles and finalist this month in Beijing to Novak Djokovic, stands provisional 12th in the chase for the last two spots in London.

Stepanek, an alternate last year when the year-ender was played in Shanghai, trails on 14th while Metz champion Monfils is 16th.

Andy Roddick clinched the sixth spot at the wrap-event last week as he rests a knee injury, joining Roger Federer, Rafael Nadal, Novak Djokovic, Andy Murray and Juan Martin Del Potro in the field.

Next in the qualifying queue is Shanghai Masters champion Nikolay Davydenko, with Spain's Fernando Verdasco and Swede Robin Soderling on his heels.

Vienna took a box-office blow as the injured and disillusioned Del Potro, who has yet to show even hints of the form which won him the US Open title over Federer, withdrew injured, returning to South America.

Cilic, 13th in the world will begin the first round at the Stadthalle with a qualifier, while Stepanek takes on Pole Lucasz Kubot, finalist last May on clay in Belgrade to Djokovic.

Monfils, one of nine retirement victims in Shanghai last week, will hope his back problems have cleared when he starts with hard-courting Spaniard Guillermo Garcia-Lopez, beaten in the Stockholm quarterfinals this week by Soderling.

The Frenchman lost the Vienna final a year ago to German Philipp Petzschner, who came out of qualifying rounds to the trophy.

Finn Jarkko Nieminen will play for his last week at the ATP level before being forced to the Challenger circuit, the result of a ranking fall to 120th after his wrist surgery absence this season.

American John Isner takes the eighth seeding with hopes that his big serve can see him through indoors. He faces a first-round match with Serb Janko Tipsarevic.