Former world number ones Rafael Nadal and Roger Federer are both outside the top four in the men's world tennis rankings for the first time in 13 years.
Spaniard Nadal, 30, is fifth in the latest ATP standings, with 35-year-old Swiss Federer two places lower.
Serbia's Novak Djokovic tops the list, ahead of Briton Andy Murray and Federer's compatriot Stan Wawrinka, with Japan's Kei Nishikori in fourth.
Nadal, who won the most recent of his 14 Grand Slams in 2014, has claimed two titles this year - in Barcelona and Monte Carlo.
Federer, a 17-time Grand Slam winner, has been out with a knee injury since Wimbledon, where he was knocked out in the semi-finals by Canada's Milos Raonic.
1 Novak Djokovic (Ser) 13,540 points
2 Andy Murray (GB) 9,845
3 Stan Wawrinka (Swi) 5,910
4 Kei Nishikori (Jpn) 4,740
5 Rafael Nadal (Spa) 4,730
6 Milos Raonic (Can) 4,690
7 Roger Federer (Swi) 3,730
8 Gael Monfils (Fra) 3,745
9 Tomas Berdych (Cze) 3,470
10 Dominic Thiem (Aut) 3,295