Novak Djokovic and Roger Federer have been drawn together in Group B for this year's ATP World Tour Finals.
The pair, who both reached the semi-finals of the Paris Masters earlier this week, are joined by former US Open champion Juan Martin del Potro.
Frenchman Richard Gasquet, who will be the lowest-ranked player competing at the event, is also in Group B.
Group A will feature David Ferrer, Tomas Berdych, Stanislas Wawrinka and world number one Rafael Nadal.
