Djokovic has a perfect record of 24 wins and no defeats in 2011
Novak Djokovic has been forced to pull out of next week's Monte Carlo Masters because of a knee injury.
The world number two had been hoping to extend his wonderful run of form, having been unbeaten in his last 26 matches, including 24 this year.
"It's a tough blow and sad news not only for the tournament and my fans but also for myself," Djokovic said.
Djokovic defeated world number one Rafael Nadal last week in the final of the Sony Ericsson Open in Miami.
That victory came two weeks after he beat the Spaniard to win the Indian Wells Masters 1000 title.
The Serbian, who resides in Monte Carlo, has been in inspired mood since
defeating Andy Murray in Melbourne to win his second Australian Open title.
He is hot on the heels of world number one Nadal in the rankings but will now miss an opportunity to close the gap in Monaco.
Djokovic has yet to confirm the extent of the injury to his knee or when he expects to return to action.
"So, it was definitely difficult decision but I had to prioritise my health," he
said on Twitter.
"Now moving on. I will be here in Monaco during the event. Will start practising during the next week, I hope."
Nadal, Roger Federer and Andy Murray are among those scheduled to play in Monte Carlo.