By Iain Rogers
MADRID (Reuters) - Clay master Rafa Nadal tamed big-serving American John Isner 7-5 6-4 to claim a place in the last eight of the Madrid Open on Thursday and was joined by Roger Federer and Andy Murray.
World number one Federer, who beat Nadal in last year's final, swatted aside Swiss compatriot Stanislas Wawrinka 6-3 6-1 and Briton Murray crushed Victor Hanescu of Romania 6-2 6-1.
Unseeded Latvian Ernests Gulbis, conquerer of Federer at last month's Rome Masters, awaits the 16-times grand slam winner in Friday's quarter-finals and third seed Murray will play Spaniard David Ferrer.
At more than two meters tall, 19th-ranked Isner is a tough opponent on any surface and two booming aces on the second and third points of the match prompted anxious muttering and nervous applause from the crowd in the Magic Box arena.
With the sliding roof closed on a rainy day in the Spanish capital, world number three Nadal struggled to make any inroads until the 11th game when he converted the first break point of the match to take a 6-5 lead.
Portuguese forward Cristiano Ronaldo and several of his Real Madrid team mates were watching in the stands as the 23-year-old Spaniard sealed victory with his only ace to set up a quarter-final against French 12th-seed Gael Monfils.
Nadal opted not to compete at last month's Barcelona Open, where he had won the previous five years, to make sure he did not suffer a repeat of the knee injuries that dogged him in 2009 after a grueling European clay season.
He appeared irritated when asked about his knees at a news conference, telling the reporter: "We've already talked enough about that. They are fine and I would prefer to talk about more pleasant topics."
"He serves well and has a very strong forehand. If he's on form he's very hard to beat."
Local favorite Fernando Verdasco was denied a place in the quarters when he was upset 7-5 6-3 by Juergen Melzer in a battle of the big-hitting left-handers.
The Spanish sixth seed, who lost to Nadal in the final in Monte Carlo and reached the last four in Rome, had treatment on an ankle problem at the end of the first set.
He committed 41 unforced errors and unseeded Austrian Melzer dashed the crowd's hopes of a possible semi-final on Saturday between Verdasco and Nadal when he broke the Madrid native for a sixth time on his first match point.
A subdued Verdasco said at a news conference he had injured the ankle in his second-round victory over Croat Ivo Karlovic but said he should be fit for the French Open.
"It's annoying, and the injury is in a difficult place," the 26-year-old said.
"There are lots of tendons in this zone but two physios have told me it isn't serious. I think I'll be able to make it for Paris and to be 100 percent."
If Nadal reaches Sunday's final, the Mallorca native will reclaim the number two ranking from Serb Novak Djokovic, who pulled out of Madrid due to illness.
(Additional reporting by Mark Elkington)
(Editing by Alison Wildey and Pritha Sarkar)