Stan Wawrinka returns to training after knee injury

World number seven Stan Wawrinka has returned to training ahead of his scheduled comeback at the Mubadala World Tennis Championship (MWTC) exhibition event in December.

Three-times grand slam winner Wawrinka, 32, last played at Wimbledon in July before withdrawing from the US Open and announcing the end of his season in August to undergo surgery following a recurring knee problem.

Serbian Novak Djokovic and world number one Rafa Nadal are also scheduled to play at the Abu Dhabi event, which starts on December 28.