Roger Federer's preparations for the French Open suffered a further blow when he was beaten in straight sets in the quarterfinals of the Rome Masters by unseeded Czech Radek Stepanek on Friday. Stepanek, who did a caterpillar dance on the clay in celebration, will face Australian Open champion Novak Djokovic after Spain's Nicolas Almagro withdrew from their quarterfinal with a wrist problem with the score at 6-1, 1-0 to the Serb. World number one Federer, struggling for consistency on clay ahead of the year's second Grand Slam later this month, was the second big gun of the day to fall to an unseeded player after his Swiss compatriot Stanislas Wawrinka won an entertaining tussle with American James Blake 6-7, 7-6, 6-1. Wawrinka will meet Andy Roddick in the semis after the American sixth seed pulled out some massive serves in a final-set tiebreaker on the way to beating Spain's Tommy Robredo 6-3, 4-6, 7-6. Federer was comfortable on his service games in the first set of the quarterfinal, taking four to love, but he failed to force any break points. Stepanek wrapped up the ensuing tiebreak 7-4 with an ace as the Swiss lost a set for the first time in the tournament. A fired-up Stepanek saved two break points in the first game of the second set and then snapped the top seed's serve immediately after. The Swiss broke back in the seventh, only to surrender his serve again the following game, a wild shot giving away the vital point. He dragged himself back in contention two games later, the counter-break coming courtesy of a beautiful backhand volley. But Federer was unable to capitalize on two mini-breaks in the tiebreak and will now have to wait at least another year for his first Rome title. Third seed Djokovic met little resistance as Almagro was hampered by a wrist problem from the early stages of their match. The Spaniard decided to stop after losing his serve in the opening game of the second set. Wawrinka, who had beaten former world number ones Juan Carlos Ferrero and Marat Safin and Andy Murray to reach the last eight, made a confident start, breaking Blake in the third game. But the American eighth seed held his nerve, broke back in the eighth game and took the first set in a tiebreak 7-5. Blake showed more resilience in the second set, saving four set points when 5-3 down and two more in the tiebreak before Wawrinka leveled the score with a sweet backhand winner down the line. Safina dumps Serena In Berlin, Russian Dinara Safina won a great scrap with fifth seed Serena Williams 2-6, 6-1, 7-6 to end the American's 17-match winning streak and reach the German Open semifinals on Friday. Safina, a surprise winner over top seed Justine Henin on Thursday, made a nervous start but found her game in the second set, as Serena started to reel off unforced errors, and went on to claim another high-profile victim in two hours 10 minutes. Ana Ivanovic, the tournament's second seed, was fighting to avoid the same fate when her match against Hungarian 10th seed Agnes Szavay was called off due to bad light. Szavay had taken the first set 6-3 and was looking strong before the Serb snatched the second with a late break 6-4. Safina now faces unseeded Victoria Azarenka of Belarus after she saw off the 15th seed Alona Bondarenko of Ukraine 7-6, 6-2. The winner of the match between Ivanovic and Szavay, which resumes on Saturday at 0900 GMT, will meet Elena Dementieva after the seventh-seeded Russian beat Jelena Jankovic, the fourth seed from Serbia, in an up-and-down 6-3, 2-6, 6-3 win. Henin out of Rome World number one Justine Henin has pulled out of next week's Rome International Tier I event due to fatigue, organizers said on Friday. The Belgian, who was knocked out of the Berlin Open on Thursday by Safina, will be replaced in the draw by Argentine Gisela Dulko. Henin received a $20,000 fine for her late withdrawal.