Rafael Nadal extended his lead at the top of the world rankings on Monday after claiming his 16th Grand Slam title at the US Open, while Roger Federer took second spot from Andy Murray.
Spaniard Nadal and 19-time major winner Federer sit first and second on the all-time Grand Slam champions list, but it is the first time they have occupied the top two places in the rankings since 2011.
Nadal, 31, had retaken the world number one spot from Murray the week before winning his third US Open title, and now holds a substantial lead over reigning Australian Open and Wimbledon champion Federer.
Swiss legend Federer, 36, was out of sorts in New York and lost to Juan Martin Del Potro in the last eight.
Murray missed the final major tournament of the season with a hip injury.
German youngster Alexander Zverev moved to a career-high ranking of fourth despite suffering a shock second-round loss to Borna Coric at Flushing Meadows.
South African Kevin Anderson, who was swept aside in straight sets by Nadal in Sunday's final, jumped 17 places to 15th, while surprise semi-finalist Pablo Carreno Busta broke into the top 10 for the first time.
ATP top 20 on September 11:
1. Rafael Nadal (ESP) 9465 points
2. Roger Federer (SUI) 7505 (+1)
3. Andy Murray (GBR) 6790 (-1)
4. Alexander Zverev (GER) 4470 (+2)
5. Marin Cilic (CRO) 4155 (+2)
6. Novak Djokovic (SRB) 4125 (-1)
7. Dominic Thiem (AUT) 4030 (+1)
8. Stan Wawrinka (SUI) 3690 (-4)
9. Grigor Dimitrov (BUL) 3575
10. Pablo Carreno Busta (ESP) 2855 (+9)
11. Milos Raonic (CAN) 2825
12. David Goffin (BEL) 2695 (+2)
13. Roberto Bautista Agut (ESP) 2525
14. Kei Nishikori (JPN) 2475 (-4)
15. Kevin Anderson (RSA) 2470 (+17)
16. Sam Querrey (USA) 2445 (+5)
17. John Isner (USA) 2425 (-2)
18. Jo-Wilfried Tsonga (FRA) 2375 (-6)
19. Tomas Berdych (CZE) 2355 (-1)
20. Nick Kyrgios (AUS) 2245 (-3)

Source: AFP