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.
For more updates on the 2012 U.S. Open, check out SB Nation's tennis hub. For score updates, check out the live scoring at the U.S. Open website.
