Roger Federer continued his trouble-free progress at the Hamburg Masters with a 6-3 6-2 win over Robin Soderling but Nikolay Davydenko and David Ferrer both fell to unseeded players.

World number one Federer, who beat Rafael Nadal to win the title for the fourth time last year, was barely made to sweat by the unseeded Swede Soderling as he reached the quarter-finals at the 2.27 million euro (£1.81 million) claycourt tournament.

Fifth seed Ferrer lost 7-6 6-2 against his Spanish Davis Cup team mate Fernando Verdasco before the fourth seeded Russian Davydenko fell 7-5 6-3 to Germany's Nicolas Kiefer in a match that brought the Hamburg crowd to their feet.

In the circumstances third seeded Serb Novak Djokovic could be well satisfied at coming through a bruising match with the Croatian Ivo Karlovic 7-6 6-3.

Djokovic, who is fast making up ground on Federer and Nadal, wasted an early break in the first set against the powerful Karlovic and almost paid the price.

The Croat moved a mini-break ahead in the tiebreak but his failure to put away a smash handed it back and Djokovic got the decisive edge with an unplayable return to feet on the next point.

The second set was easier for the Serb, who looks in great shape after winning in Rome last week and can look forward to a quarter-final against Spain's Albert Montanes.

"Karlovic has one of the most difficult serves to face on any surface," said Djokovic. "I thought that on clay I would have more chances to return it but I was wrong."

Federer was equally happy after outclassing Soderling in just 63 minutes.

"I controlled things from the baseline and I served well when I had to," Federer said. "He has a big game, a big serve, but I retrieved it well and scrambled well. That was important."

Federer's next opponent will be Verdasco after his surprise victory over Ferrer in the first match on centre court.

The Spaniard edged the first set 7-4 in the tiebreak and took a 4-1 lead in a second set that was tighter than the scoreline suggests, with Ferrer scrapping for everything.

Reuters