Novak Djokovic Faces Challenge to Qualify for ATP Finals

• Novak Djokovic aims to qualify for the ATP Finals despite a limited schedule.
• Djokovic won the China Open but suffered a first-round loss at the Shanghai Masters.
• Greg Rusedski believes Djokovic can still qualify for the ATP Finals.
• Djokovic's chances are now uncertain due to his recent performance.
• The ATP Finals is the year-end tournament Djokovic is targeting.