World number one Serena Williams was forced to pull out of her Hopman Cup encounter earlier today because of a knee complaint.
The American had been due to face Ukraine's Elina Svitolina at the Perth-based tournament.
However, having suffered with some inflammation to the joint during a recent training session, Williams decided to withdraw and was replaced by Vicky Duval.
It is not expected that the problem will prevent the 34-year-old from defending her Australian Open title later this month.
| ATP Rankings | Points | ||
| 1 |  | Novak Djokovic | 15,550 |
| 2 |  | Andy Murray | 7,925 |
| 3 |  | Roger Federer | 7,535 |
| 4 | | Stanislas Wawrinka | 6,460 |
| 5 |  | Rafael Nadal | 5,915 |
| 6 |  | Kei Nishikori | 4,290 |
| 7 |  | Jo-Wilfried Tsonga | 3,400 |
| 8 |  | Tomas Berdych | 3,120 |
| 9 | | David Ferrer | 3,010 |
| 10 |  | Milos Raonic | 2,740 |
| 11 |  | Marin Cilic | 2,680 |
| 12 | | Richard Gasquet | 2,635 |
| 13 |  | David Goffin | 2,605 |
| 14 |  | Dominic Thiem | 2,480 |
| 15 | | Gael Monfils | 2,460 |
| 16 |  | John Isner | 2,235 |
| 17 | | Roberto Bautista Agut | 2,015 |
| 18 | | Gilles Simon | 1,900 |
| 19 |  | Kevin Anderson | 1,840 |
| 20 | Benoit Paire | 1,766 | |
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