Hamburg, Germany -- (Sports Network) - The world's top-three stars -- Swiss Roger Federer, Spaniard Rafael Nadal and Serbian Novak Djokovic -- were all straight-set third-round winners Thursday at the $2.955 million Masters Series Hamburg, a clay-court French Open tuneup.

The top-seeded reigning Hamburg champion Federer drilled Swede Robin Soderling for a sixth straight time, 6-3, 6-2, while the second-seeded three- time French Open titlist Nadal handled 15th-seeded Brit Andy Murray by an identical 6-3, 6-2 score, and the third-seeded Australian Open champion Djokovic got past 6-foot-10 Croat Ivo Karlovic 7-6 (7-3), 6-3 on Day 5 at Rothenbaum. The high-flying Djokovic was last week's clay-court champ in Rome.

The reigning Wimbledon and U.S. Open champion Federer beat the clay-court king Nadal in last year's Hamburg finale to record his fourth title here in six years (2002, 2004-05, 2007). Nadal topped Federer in a clay-court finale in Monte Carlo just last month.

Nadal must finish one round better than Djokovic this week in order to retain his world No. 2 ranking.

Federer's quarterfinal opponent on Friday will be Spanish lefthander Fernando Verdasco, while Nadal will encounter his good friend, 11th-seeded Spaniard Carlos Moya, and Djokovic will meet unseeded Spaniard Albert Montanes. Verdasco toppled fifth-seeded fellow Spaniard David Ferrer 7-6 (7-4), 6-2, while Moya edged out fellow former world No. 1 Marat Safin, of Russia, 6-2, 6-7 (3-7), 6-1, and Montanes mauled Serbian Janko Tipsarevic 6-2, 6-1. Safin, a rare qualifier this week, reached finals here back in 2000 and 2002.

Friday's other quarter will pit heavy German crowd favorite Nicolas Kiefer against Italian Andreas Seppi, as Kiefer upended fourth-seeded Russian Nikolay Davydenko 7-5, 6-3 and Seppi knocked off 12th-seeded Argentine Juan Monaco 6-0, 6-3.