Roger Federer and Rafael Nadal eased through to the quarter-finals of the Qatar Open despite unusually windy conditions in Doha.
Defending champion Federer beat Slovenian qualifier Grega Zemlja 6-2 6-3 to set up a meeting with Italian Andreas Seppi.
World number two Nadal beat Germany's Denis Gremelmayr, also a qualifier, 6-2 6-2 and will now meet Mikhail Youzhny.
French seeds Jo-Wilfried Tsonga and Gael Monfils also made progress.
Third seed Tsonga saved two set points in the first set and went on to beat Italy's Flavio Cipolla 7-6 (10-8) 6-3, while Monfils, seeded fourth, overcame Benjamin Becker 7-5, 4-6, 7-5.
Federer's victory was his 19th in a row - his last defeat came in the semi-finals of the US Open when he was ousted by Novak Djokovic.
"It can be tricky when you enter the first tournament of the season and right away you play an incredibly tough three-setter," Federer said.
"The body feels that, and that's why I'm happy to be through into the quarter-finals without too much trouble."
Nadal's win could have been more comprehensive than it was as he spurned 11 of his 15 break point opportunities.
"I'm trying to play aggressive, I'm trying to return a little bit better, because for me the worst thing I did for most of last year was the return, especially the second half of the year," Nadal said.
"I'm so happy with my returns here and happy how a few things have worked well with the new weight of the racket. I'm starting to have good feelings, so that's really important."
Seeded players were well on top as Viktor Troicki (5) beat Matthias Bachinger 7-6 (8-6) 6-1, Youzhny (7) beat Ivo Karlovic 6-2 6-7 (3-7) 6-3 and Seppi (8) saw off the challenge of Guillermo Garcia-Lopez 7-5 6-3.
A full complement of seeded players in the last eight was spoiled as sixth seed Alex Bogomolov Jr withdrew with an ankle injury and Spaniard Albert Ramos, ranked 66 in the world, went through on a walkover.