Spain's Rafael Nadal, the top seed, had to fight hard to beat Germany's Tobias Kamke 6-3, 6-7 (3-7), 6-3 Wednesday to advance to the quarterfinals at the Qatar ExxonMobil Open.
The tournament's No. 2 seed, Spain's David Ferrer, third-seeded Andy Murray of Britain and Spain's Fernando Verdasco, the No. 8 seed, were all knocked out of the tournament.
Nadal needed two hours and 24 minutes to beat Kamke and advance to the quarters, where he will meet Latvia's Ernests Gulbis on Thursday.
Germany's Daniel Brands beat Ferrer 6-4, 7-5, while another German player, Florian Mayer, defeated Murray 3-6, 6-4, 6-2.
Romania's Victor Hanescu took out Verdasco 4-6, 7-6 (7-0), 6-2.
Nadal, the world No. 1, got off to a better start than in his earlier match in Doha, and was up 4-1 just 17 minutes into the match, hitting 73 percent of his first serves.
The Spanish star took the first set in 35 minutes from Kamke, who he had never played before.
Kamke took his game up several notches in the second set, breaking Nadal in the fourth game.
The German, who had not lost any points on serve in his first match, but Nadal broke back and took the set to a tiebreaker.
Kamke, however, did not fall apart and managed to tiebreaker.
Nadal and Kamke played evenly in the third set until the eighth game, when the Spaniard took advantage of the German's sixth double fault to get a break and put the match away.
Gulbis, the No. 7 seed and Nadal's next opponent, beat Poland's Lukasz Kubot 6-2, 4-6 y 6-3.
In other action, Germany's Peter Gojowczyk beat countryman Philipp Kohlschreiber 7-6 (7-4), 7-6 (9-7), while Germany's Dustin Brown defeated Croatia's Ivo Karlovic 3-6, 7-6 (15-13), 6-4.