The 12-time Grand Slam champion has been struggling with an elbow injury and will drop out of the world's top 10 next week for the first time since March 2007.

The Serb has not played since retiring from his Wimbledon quarter-final against Tomas Berdych four months ago.

"Novak pulled out, but he hasn't been playing for two and a half months," Forget said on Friday after Rafael Nadal's withdrawal from his tournament in Paris.

"When he (Djokovic) came to see me last Saturday he said, 'I played twice since I stopped, with my left hand'."

Djokovic said last month he was hoping to return to action at the exhibition World Tennis Championship in Abu Dhabi next month.

Current world number one Nadal pulled out before his quarter-final in Paris with a knee injury, leaving Marin Cilic as the only Grand Slam champion left in the draw after Roger Federer also withdrew before the start of the tournament.