World number two Novak Djokovic reached a perfect 25-0 winning record this season with a second-round victory at the Serbia ATP Open, beating Romanian qualifier Adrian Ungur on Wednesday.
With his 25th victory Djokovic registered the best start to an ATP tour season since Ivan Lendl in 1986.
After beating Ungur 6-2, 6-3 in less than 70 minutes on the clay, the Australian Open victor and local crowd favourite said: "I want to thank the audience for attending the game in pouring rain.
"The most beautiful thing is to play before a domestic audience. I lost the service in the fifth game of the first set, but this is my first match on the claycourt."
The 23-year-old Djokovic's quarter-final opponent on Friday will be Slovenian Blaz Kavcic.
Djokovic said he had lost against Kavcic when he was 14.
"This is my chance for revenge," Djokovic joked.
At the start of the Serbia Open, Djokovic said was confident he could pass the supreme claycourt test by beating Rafael Nadal on the Spaniard's favourite surface.
Djokovic, who earlier this month was forced to pull out of the Monte Carlo Masters blaming a knee injury, said he was not burdened by a record-start to the season.
However, the number two said he had an ambition to win at least one more Grand Slam this year and get himself involved in fight for the number one position.
Since the start of the season, Djokovic won titles also at the Australian Open, Dubai and Indian Wells.
He was his country's key player as he led Serbia to their first-ever Davis Cup title in Belgrade last December.