INQUIRER Sports

LONDON - Roger Federer will face US Open champion Juan Martin del Potro, Andy Murray and Spain's Fernando Verdasco in the tougher of the two round robin groups for the ATP World Tour Finals here.

Group B in the end-of-season showpiece event features former world number one Rafael Nadal, recent Paris Masters champion Novak Djokovic, Nikolay Davydenko and late-entrant Robin Soderling.

Soderling had failed to qualify for the eight-man event but was brought in following the withdrawal of Wimbledon finalist Andy Roddick, who has not played since injuring his left knee in Shanghai last month.

Frenchman Jo-Wilfried Tsonga is now on standby in case of any other withdrawals.

The top two players in each of the round robin groups advance to the semi-finals of the tournament, which starts Sunday at London's O2 Arena. The final is on November 29.