updated 2:41 p.m. ET Aug. 28, 2008

NEW YORK - Venus Williams kept favorites on the fast track at the U.S. Open, overwhelming Rossana de Los Rios of Paraguay in less than an hour to reach the third round on Thursday.

The seventh-seeded Williams won on her fifth match point after 59 minutes.

That's mostly been the pattern so far at Flushing Meadows, with the big names facing little trouble.

Through the early action on Day 4, only two top players had been upset in the tournament - No. 8 Vera Zvonareva and No. 10 Anna Chakvetadze.

No. 6-seeded Dinara Safina, No. 9 Agnieszka Radwanska, No. 17 Alize Cornet, No. 18 Dominika Cibulkova and No. 19 Nadia Petrova also won in straight sets, while No. 20 Nicole Vaidisova lost to Severine Bremond 7-5, 6-3.

Venus Williams breezed past an opponent ranked 117th. After teaming with her sister to win Olympic gold in doubles, the two-time U.S. Open champion stayed on course to play Serena in the quarterfinals here.

Safina, not nearly as volatile as brother Marat Safin, played under control in beating Roberta Vinci of Italy 6-4, 6-3. The Russian seemed perturbed just once, when she challenged a line call - she was right - and earned a replay of a point late in the second set.

The 22-year-old Safina has won 17 of her last 18 matches, losing only to Elena Dementieva for the Olympic gold medal.

Radwanska beat Mariana Duque Marino of Colombia 6-0, 7-6 (3) and fittingly won the final point at the net. Last year, the Polish teen made a splash at the U.S. Open when she startled Maria Sharapova, often walking halfway to the service box and hopping before backing up to receive.

That breakthrough win over Sharapova came in the third round. This time, Radwanska will play Cibulkova in the third round.

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Cornet rallied in the first-set tiebreaker to fashion a 7-6 (5), 6-1 over Bethanie Mattek of the United States. The 18-year-old French teen took advantage of Mattek's four straight misses to close out the opening set.

Mattek is known for her outlandish outfits - she started out last year's Open in a revealing, metallic gold Wonder Woman get-up and later wore a leopard-print ensemble. Her attire for this match was downright conservative by her standards, featuring a white top that was wide open in the back and a black skirt.

Now ranked No. 44 after a successful season, Mattek lost in her first matchup with Cornet. Mattek came to the Open without a coach and sometimes uses YouTube to scout players she's never faced.

Cornet stayed aggressive, highlighted by a sequence in the first set when she hit so many overhead slams in succession, the linesman keep retreating to give Mattek more room to maneuver.