World number one Novak Djokovic overcame a first set slump to beat Serbian countryman Viktor Troicki and reach the Paris Masters quarterfinals here on Thursday. Djokovic, who has been battling a shoulder injury, was broken twice in the first set and folded on Troicki\'s first set point when he drove a backhand into the net. The top seed went 2-0 up in the second set, only for Troicki to level, but Djokovic broke again to go 4-2 ahead before levelling the match. After that, Djokovic never looked back. \"It was a difficult match,\" said Djokovic. \"I still wasn\'t maybe where I\'d want to be with my shoulder, but I pulled out a good performance in the end.\" \"It\'s never easy to play someone you know well, who\'s your friend off the court, but a win is a win today.\" Djokovic will meet sixth seed Jo-Wilfried Tsonga, the 2008 champion, for a place in the semifinals after the Frenchman overcame Italy\'s Andreas Seppi 6-3, 6-4.