Novak Djokovic into Serbia Open final after walkover

Novak Djokovic
Djokovic has not lost since the ATP Finals in London last November

Novak Djokovic reached the Serbia Open final after fellow Serb Janko Tipsarevic withdrew before their semi-final with a thigh injury.

Djokovic, who has not lost since the ATP Finals in London last November, did not even hit a ball against Tipsarevic, who pulled out before the game started.

The walkover extended the world number two's record to 26-0 in 2011 ahead of Sunday's final against Feliciano Lopez.

The Spaniard beat Filippo Volandri 7-6 (7-3) 6-2 in the other semi-final.

"Bad news. Janko had to pull out from tonight's semi-final match because of a muscle injury," Djokovic wrote on his Facebook page. "I sincerely hope he will manage to recover for the rest of the clay-court season."

Djokovic will start as the strong favourite against world number 37 Lopez, having won all three of their previous meetings, the latest en route to his 2011 Dubai Championships title in February.

Meanwhile, Juan Martin del Potro defeated Uruguay's Pablo Cuevas on Saturday at the Estoril Open in Portugal. The Argentine won 6-2 7-6 in one hour and 49 minutes to book his place in Sunday's final.

Del Potro, currently 46th in the world following his lengthy injury lay-off last year, broke Cuevas's serve in the first game and had opened up a 4-2 lead when a heavy rain shower suspended play.

But del Potro quickly wrapped up the first set when they resumed before saving set point to clinch the match on a tie-break, handing him a chance of lifting his ninth tour-level title.

In the final, Del Potro will face number two seed Fernando Verdasco of Spain, whose semi-final opponent Milos Raonic of Canada retired while trailing 6-4.