Berlin - Spaniard Rafael Nadal continued to top the latest men's world tennis rankings which were released Monday by the ATP.
Nadal has 13 310 points while Serbia's Novak Djokovic remains his closest pursuer on 11 040.
David Ferrer, who defeated Nadal in the quarter-finals in the Monte Carlo Masters last week, moved up one place to fifth.
Frenchman Richard Gasquet dropped out of the top 10 as Milos Raonic and John Isner both gained one spot at his expense.
Meanwhile, South Africa's Kevin Anderson has remained inside the top-20 on 1 800 points.
ATP top 10 as of April 21 (previous ranking in parenthesis):
1. Rafael Nadal (ESP) 13 730 pts2. Novak Djokovic (SRB) 11 040
3. Stanislas Wawrinka (SUI) 6 580
4. Roger Federer (SUI) 5 805
5. David Ferrer (ESP) 4 910 (+1)
6. Tomas Berdych (CZE) 4 720 (-1)
7. Juan-Martin Del Potro (ARG) 4 215
8. Andy Murray (GBR) 4 040
9. Milos Raonic (CAN) 2 715 (+1)
10. John Isner (USA) 2 555 (+1)
11. Richard Gasquet (FRA) 2 545 (-2)
12. Jo-Wilfried Tsonga (FRA) 2 370
13. Fabio Fognini (ITA) 2 190
14. Tommy Haas (GER) 2 075 (+2)
15. Mikhail Youzhny (RUS) 2 065
16. Grigor Dimitrov (BUL) 2 040 (-2)
17. Kei Nishikori (JPN) 1 985
18. Tommy Robredo (ESP) 1 980
19. Kevin Anderson (RSA) 1 800
20. Nicolas Almagro (ESP) 1 750