Novak Djokovic (L) of Serbia hugs compatriot Viktor Troicki following their match at the Indian Wells ATP tennis tournament in Indian Wells, California March 16, 2011.  [Photo/Agencies]

INDIAN WELLS, California - Australian Open champion Novak Djokovic extended his perfect record this season to 15-0 by pounding his fellow Serb Viktor Troicki 6-0 6-1 to reach the quarter-finals at Indian Wells on Wednesday.

Although Djokovic needed five match points before sealing victory in 66 minutes, he outclassed his good friend and doubles partner with a superb display of sliced backhands, crunching top-spin forehands and delicate drop shots.

With late afternoon shadows lengthening on the showpiece stadium court, he ended the match with a rasping backhand winner down the line before saluting the crowd by raising both arms skywards.

"I am playing probably the best tennis of my life these last three months," Djokovic, 23, said courtside. "And it all started with the Davis Cup win (in December's final) where Viktor was a hero.

"Viktor is one of my best friends, on and off the court, but one of us has to lose. It was tough playing him. He's somebody I grew up with, was part of my team at the Davis Cup and in juniors."

Djokovic, who claimed his second grand slam crown at the Australian Open in January and his 20th ATP title at last month's Dubai championships, broke Troicki three times to sweep through the first set.

He again broke his opponent in the fourth and sixth games of the second before the two Serbs treated the stadium crowd to some of the best rallies of the match in a protracted final game.

Djokovic, champion here as a 20-year-old in 2008, will face either American eighth seed Andy Roddick or Frenchman Richard Gasquet in the quarter-finals.

Earlier, Spaniard Tommy Robredo and former US Open champion Juan Martin del Potro of Argentina also booked their places in the last eight.

Hamstring Strain

Robredo, despite being hampered by a hamstring strain, crushed American Sam Querrey 6-1 6-3 and del Potro came from 1-6 down in the second set tiebreak to beat Philipp Kohlschreiber 7-6 7-6.

Former world number five Robredo broke an out-of-sorts Querrey three times in the opening set and once in the second to improve his record this year to 16-4.

Under overcast morning skies at the Indian Wells Tennis Garden, the Spaniard struggled with his leg late in the second set and was delighted to have a day's rest before Friday's quarter-finals.

"Hopefully it's going to be alright," 25th seed Robredo said after grunting and groaning his way to victory from the baseline. "I have had this pain for a month already and in the fourth game of the second set, I felt a strain.

"Luckily I could win," the Spaniard told reporters later, speaking through an interpreter. "And now I have one day to recover, and hopefully I can go through."

Del Potro, who played just three tournaments last year because of a wrist injury, sealed victory with his 13th ace of the match after the German had netted a forehand on the previous point.

"It is not normal to come back from 6-1 down on tiebreaks but I got lucky and I take my opportunities," said the Argentine who won his eighth ATP title at last month's Delray Beach International Championships.

Later on Wednesday, world number one Rafa Nadal was scheduled to take on Indian qualifier Somdev Devvarman while second-ranked Roger Federer was pitted against American wildcard Ryan Harrison.