Cape Town - Serbian star Novak Djokovic has dropped out of the top four in the ATP Tour rankings for the first time in a decade.
The new rankings published on Monday sees the former world number one fall to fifth spot while Stan Wawrinka of Switzerland climbs to fourth place.
The 30-year-old Serb, who had been ranked inside the top four since July 2007, has been forced to miss the rest of the year in order to recover from a right elbow injury that has been troubling him for the last 18 months or so.
Britain's Andy Murray remains world number one, but his ranking will be under threat from Spain's Rafael Nadal when the two compete in Toronto next week.Latest Top 20 ATP Tour rankings:1. Andy Murray (GBR) 7 7502. Rafael Nadal (ESP) 7 465
3. Roger Federer (SUI) 6 545
4. Stan Wawrinka (SUI) 5 780
5. Novak Djokovic (SRB) 5 325
6. Marin Cilic (CRO) 5 065
7. Dominic Thiem (AUT) 4 020
8. Kei Nishikori (JPN) 3 140
9. Milos Raonic (CAN) 3 130
10. Alexander Zverev (GER) 3 060
11. Grigor Dimitrov (BUL) 2 980
12. Jo-Wilfried Tsonga (FRA) 2 805
13. David Goffin (BEL) 2 515
14. Tomas Berdych (CZE) 2 390
15. Pablo Carreno Busta (ESP) 2 350
16. Roberto Bautista Agut (ESP) 2 245
17. Lucas Pouille (FRA) 2 210
18. John Isner (USA) 2 205
19. Jack Sock (USA) 2 155
20. Nick Kyrgios (AUS) 1 930