(CNN) -- The top three seeds, Rafael Nadal, Roger Federer and Andy Murray are all through to the quarterfinals of the Qatar Open in Doha after comfortable straight sets victories on Wednesday.
Murray was a study in concentration as he easily accounted for his German opponent in Doha.
Defending champion Murray, the world No.4, continued his unbeaten start to 2009 with a 6-2 6-4 win over Germany's Philipp Petzschner.
Murray, who had brushed aside Spain's Albert Montanes in his opening round match, found a tougher opponent in 24-year-old Petzschner but was never seriously troubled.
He broke in the third game of the first set on his fifth break point and a further break saw him to a 5-2 lead before serving out for the opener.
The second set was followed a similar pattern, with 2008 U.S. Open finalist and third seed Murray taking his opponent's service in the third game.
He wrapped up victory with the second of three match points in the 10th game.
Top seed Nadal is also through after taking advantage of an error-strewn performance from Karol Beck of Slovakia to go through 6-1 6-2.
Beck committed 27 unforced errors as Nadal cruised into a last eight showdown with fifth-seeded Frenchman Gael Monfils, who saw off Nicolas Devilder of France 7-5 7-6.
Second seed Federer defeated Andreas Seppi 6-3 6-3 -- with the Italian committing 31 unforced errors, two more than the former world number one, in a disappointing match.
Murray lost to Federer in the U.S. Open final last September but, unlike Nadal and Federer, Murray was not broken in his match.