On July 4th Djokovic had 16,950 pts and Murray had 8,915, 8000 point swing in 4 months 
The form difference between these 2 players since the French Open is incredible to make 8000 point evaporate, Djokovic has fallen off of a cliff.
Since the French Open
Djokovic - lost 3rd round at Wimbledon, Won Canada (Murray skipped it), lost 1st round Olympics, lost US Open Final, lost SF Shanghai, lost QF Paris.
Murray - Won Queens, Won Wimbledon, Won Olympics, lost Cincy final, lost US Open QF, Won Beijing, Won Shanghai, Won Vienna, in final of Paris vs Isner.

The form difference between these 2 players since the French Open is incredible to make 8000 point evaporate, Djokovic has fallen off of a cliff.
Since the French Open
Djokovic - lost 3rd round at Wimbledon, Won Canada (Murray skipped it), lost 1st round Olympics, lost US Open Final, lost SF Shanghai, lost QF Paris.
Murray - Won Queens, Won Wimbledon, Won Olympics, lost Cincy final, lost US Open QF, Won Beijing, Won Shanghai, Won Vienna, in final of Paris vs Isner.