BELGRADE, Serbia - Novak Djokovic cruised to his 25th consecutive win this season by beating Romanian qualifier Adrian Ungur 6-2, 6-3 in his clay court opener in the second round of the Serbia Open on Wednesday.

Related readings: Djokovic crushes Nadal to win Miami Masters  Unstoppable Djokovic lifts Indian Wells title

The No 2-ranked Serb is off to the best start to a season since Ivan Lendl swept his first 25 matches in 1986. He has won 61 of 67 sets and four tournament titles on three continents, including the Australian Open, to take the No. 2 ranking from Roger Federer - the last player to beat him.

On Wednesday, Djokovic was broken twice in front of his home crowd but was never really troubled by Ungur.

"It's tough to play on clay after almost a year," Djokovic said. "It will take a bit to get used to it."