World number two Novak Djokovic stretched his unbeaten run this year to 25 matches after reaching the Serbia Open third round with a 6-2 6-3 win over Romanian Adrian Ungur on Wednesday.
The 23-year old Serb, who was given a first-round bye in the tournament organised by his family, looked rusty at times in his first match since he won the Miami Masters on April 3 and dropped serve twice in light drizzle on a windy evening.
Coming off an impressive run in which he also captured the Australian Open, the Dubai Championships and the Indian Wells Masters, Djokovic hit just one ace and only 59 percent of his first serves.
Having raced into a 3-0 lead in the opening set, the home crowd favourite allowed world number 175 Ungur to make it 3-2 with a break of serve before he moved up a gear and won six of the next seven games.
The Serb hit several trademark winners in the closing stages of the second set, drawing a warm round of applause from around 4,000 fans who turned up at Belgrade's tennis complex built by the banks of Danube River.
Djokovic, who won the inaugural tournament in 2009 but retired in the early stages last year with illness, meets Slovenian Blaz Kavcic for a semi-final berth.