By Iain Rogers
MADRID (Reuters) - World number one Rafa Nadal moved into the quarter-finals of the Madrid Open without hitting a shot on Thursday after his third-round opponent Juan Martin Del Potro withdrew from the clay event with a hip injury.
The Spanish top seed was joined in the last eight by in-form Serb Novak Djokovic and Swiss former world number one Roger Federer, the second and third seeds, who breezed past Guillermo Garcia-Lopez and Xavier Malisse respectively.
Djokovic took his winning streak since the beginning of the year to 29 matches with a 6-1 6-2 success against Spaniard Garcia-Lopez, equaling Ivan Lendl's mark from 1986, the third best season start on record after John McEnroe in 1984 (42) and Bjorn Borg four years earlier (33).
Federer, who had to save a match point to get past Feliciano Lopez on Wednesday, beat Belgian Malisse 6-4 6-3.
Fourth seed Andy Murray failed to make the last eight on his return from an elbow injury when he was upset 6-4 6-2 by unseeded Brazilian Thomaz Bellucci.
Djokovic was pleased to have matched Lendl's streak.
"I am very flattered to be able to have the same amount of wins as this tennis legend but it's not something I think about," he told a news conference.
"It's the least of my priorities. I just want to keep on winning and that's what it's all about."
Briton Murray, who was sidelined for last month's Barcelona Open, was broken once in the first set and twice in the second by stylish left-hander Bellucci in the pair's first meeting.
Ranked 36, Bellucci will play Tomas Berdych on Friday for a place in the last four of the clay event after the Czech seventh seed beat Argentine Juan Monaco 7-5 6-3.
Fifth-seeded Swede Robin Soderling, the last man to beat Nadal on clay back in 2009 at the French Open, came through his third-round match against Frenchman Jo-Wilfried Tsonga 7-6 7-5 and will play Federer on Friday for a place in the last four.
The 24-year-old Mallorcan has a phenomenal record on clay since 2005 of 187 wins and only six defeats and is the defending champion at the Magic Box arena in the Spanish capital.
His opponent in the last eight will be unseeded Frenchman Michael Llodra, who saw off Spanish qualifier Daniel Gimeno-Traver 1-6 6-4 7-6.
Djokovic will face David Ferrer, runner-up to Nadal in the Monte Carlo and Barcelona finals, after the Spanish sixth seed overcame Sergiy Stakhovsky of Ukraine 6-3 7-6.
(Editing by Martyn Herman and Mark Meadows)