The Williams sisters got blown out in the first set of a loss on Monday to the fourth-ranked pair Maria Kirilenko and Nadia Petrova of Russia, and never recovered.
Serena Williams and Venus Williams were completely overmatched in the first set, losing 6-1. The Williams sisters had eight unforced errors compared to one for Kirilenko/Petrova. The second set was a bit more competitive, but the Williams sisters still fell short, 6-4. They were once again done in by unforced errors -- racking up another 11, as opposed to just two for Kirlenko/Petrova.
Elsewhere on the women's side, world No. 20 Roberta Vinci upset the second-seeded Agnieszka Radwanska on Monday afternoon to advance to the quarterfinals of the 2012 U.S. Open.
With the victory, Vinci has now advanced farther than any Italian in singles at a major tournament.
On the men's side, Marin Cilic of Croatia had to fight tooth and nail through the first two sets of a three-set victory against Martin Klizan of Slovakia. Cilic took complete control in the third set, but the first two could have gone either way. Cilic advances after winning 7-5, 6-4, 6-0.
Cilic proceeds to the quarterfinals, and will face the winner of the match between third-seeded Andy Murray and 15th-seeded Milos Raonic. Murray won the first set against Raonic, 6-4, and the two are currently in the beginning of the second set.