Nadal progresses through to the quarter-final
Rafael Nadal and Roger Federer reached the Madrid Open quarter-finals with contrasting victories.
Spanish world number two Nadal came through a tricky encounter against big-serving American John Isner 7-5 6-4.
In the late match, top seed Federer had an easier time in seeing off fellow Swiss Stanislas Wawrinka 6-3 6-1.
Nadal's countryman, sixth seed Fernando Verdasco - a semi-finalist at the Rome Masters - suffered a surprise 7-5 6-3 loss to Austrian Jurgen Melzer.
In a tie featuring nine breaks of serve, Verdasco, who received lengthy treatment on an ankle problem, was ousted by the world number 30.
Verdasco refused to blame his injury for the defeat, admitting he had been outplayed.
"That isn't the only reason for having lost, I think many other factors played into it," said Verdasco.
"I haven't played indoors for months and I've never had the opportunity to train here with the roof closed - I think it gave him the advantage as he's more of an indoor player than an outdoor player.
"But I think he deserved to win more than I did, he played better than me."
Melzer will now play another Spaniard, Nicolas Almagro who followed up his shock win over fourth seed Robin Soderling in the second round with a 6-4 6-1 defeat of Argentina's Juan Monaco.
Nadal, champion in 2005 when the event was played on indoor hardcourts, held Isner to 11 aces on the clay of the Caja Magica.
Federer (right) and Wawrinka won Olympic doubles gold in 2008
The four-time French Open winner broke Isner late in the first set and early in the second to cement his 12th consecutive clay victory of the season.
"It was a very dangerous and difficult match and I played well," Nadal said.
"When I had chances with the return I took them. For me it was a very important victory."
He now faces French 12th seed Gael Monfils, a 7-6 (7-5) 6-4 winner over Guillermo Garcia-Lopez.
"Gael is a charismatic player, he plays fast and aggressive. He can change strategy suddenly and is very confident," Nadal added.
Federer was pleased with his victory over Davis Cup team-mate Wawrinka, saying: "I'm very happy with how I played.
"To beat Stan on his best surface is excellent. I'm feeling great about my play now."
Federer now faces Latvian Ernests Gulbis who beat Feliciano Lopez 6-2 7-6 (7-0) in Madrid and defeated the world number one in Rome last month.
In the women's event, Jelena Jankovic, Samantha Stosur and Li Na avoided joining the lengthy list of seeds to bow out of the tournament.
Eleven of the 16 seeds are already out, with number four Venus Williams the only surviving member of the top six.
Seventh seed Jankovic cruised past Anabel Medina Garrigues 6-2 6-0 in her third-round match, while number eight Stosur defeated veteran Swiss Patty Schnyder 7-6 (7-3) 6-2.
Australian Stosur will now play Venus Williams in the quarter-finals.
China's Li, the 13th seed, beat Alona Bondarenko 6-3 6-4 and will face Shahar Peer, who defeated Arantxa Parra Santonja 7-5 6-2.
The only seed to fall on Thursday was number eight Nadia Petkovic, who could not follow up her win over Serena Williams as she slumped to a 6-4 7-6 (8-6) loss to Aravane Rezai, who now plays Jankovic.