Nadal on a roll

Rafael Nadal and Novak Djokovic will meet for the third time in as many Masters events on Saturday after the duo swept to straight-sets quarterfinal wins in Madrid on Friday.

World number one Nadal surprisingly trailed 0-4 in the second set against Spanish rival Fernando Verdasco, the seventh seed, but the king of clay stormed back for a 6-4, 7-5 win in a shade under two hours.

Third seed Djokovic, fighting to claw back his number three ranking from Scot Andy Murray, will again face Nadal on clay after losing to the Spaniard in the finals at Monte Carlo and Rome over the past month.

The Serbian reached his fourth consecutive Masters semifinal with a 6-4, 6-4 win over Croatian wild card Ivan Ljubicic.

Nadal said he was happy to have avoided a third set.

"I thought at that moment (when he trailed 0-4) that I had to play a bit better and get more confidence for a possible third set," said Nadal. "I played really bad at that moment."

Murray's hopes of celebrating his 22nd birthday with a victory were dashed by Argentine fifth seed Juan Martin Del Potro who beat the Scot 7-6 (7/4), 6-3 in a late-night match-up.

Del Potro, who had lost all three of his previous meetings with Murray, came back from 2-5 in the first set to claim victory on a fourth match point in the ninth game of the second.

The Argentine now tackles Roger Federer who was made to work before overcoming Andy Roddick 7-5, 6-7 (5/7), 6-1, his 18th career win over his old American rival.

Nadal has now won 32nd consecutive matches on clay, a run stretching back to May last year when he lost to compatriot Juan Carlos Ferrero in the second round in Rome.

The world number one stands 18-0 on clay this year with Monte Carlo, Barcelona and Rome trophies already claimed.

Since 2005, Nadal has compiled a remarkable 149-4 match record on clay, a run which includes four successive French Open titles.

After surrendering his 4-0 second set lead, Verdasco then saved two match points in the 10th game before Nadal eventually claimed victory with a concluding break on the first of three more match points.

Federer last lost to Roddick in Miami last year, a result which ended an 11-match winning streak. But the American has now lost three times in 2009 to the Swiss.

From a total of 20 career meetings, Federer has prevailed 18 times.

"I should have won in straights, but that's what happens sometimes when you play Andy. I bounced back in the third and played well," said Federer, still in search of his first trophy of 2009.

"I came up with some nice points. Those make me happy. I'm pleased with how I played."

Roddick was not unhappy with his first few days on clay after missing six weeks of the season to get married to US swimsuit model Brooklyn Decker.

"I got into two pretty tough matches here," said the former world number one, who has always had troubles on clay.

"Coming back after six weeks off on probably my least favourite surface could be worse.

"All in all, it was pretty good preparation and hopefully it can get better too. I have definitely felt worse going into the French Open before."