LONDON, (Reuters) – World number one Roger Federer  will face his U.S. Open conqueror Juan Martin del Potro in the  round-robin stage of the ATP Tour finals after getting the rough  end of yesterday’s draw for the season finale.

The Swiss, still not guaranteed to end the year on top of  the rankings, will also face Britain’s Andy Murray and Spain’s  Fernando Verdasco in Group A at the eye-catching O2 Arena  alongside the River Thames when play starts on Sunday.

Rafael Nadal, who missed last year’s event in Shanghai and  therefore has no ranking points to defend, has the easier draw  as he attempts to topple Federer from the world number one spot.