Novak Djokovic has pulled out of next week's Monte Carlo Masters through injury. The world No 2, who is unbeaten this year with 24 straight wins, has a knee problem.
"It is a very sad moment not only for this tournament and my fans, but also for myself," the 23-year-old said in a statement on his official website.
"This is my favourite tournament and my home event. Monte Carlo is where I spend most of my time away from the circuit and this is my club where I practice and train all year long. Unfortunately I had to take this decision to withdraw."
The Serbian has won tournaments in Dubai, Indian Wells and Miami since taking the Australian Open title in January.
Meanwhile, former world No 1 Dinara Safina was forced to abandon her quarter-final against top seed Victoria Azarenka at the Andalucia Tennis Championships yesterday because of a lower back injury.
Azarenka of Belarus, winner in Miami last week, was leading 5-1 when Russian Safina, who has slipped to 81 in the rankings, retired from the event in Marbella.