MIAMI, March 30 (Reuters) - Danish teenager Caroline Wozniacki upset Russian fourth seed Elena Dementieva 7-5 6-4 to reach the Sony Ericsson Open quarter-finals on Monday.
The 18-year-old from Odense came back from a break down in each set to reach her sixth quarter-final of the season.
The result continued a poor tournament for the top East European women with Russians Dinara Safina and Vera Zvonareva and Serbians Jelena Jankovic and Ana Ivanovic, all top-10 players, failing to make the last 16.
Wozniacki, named the WTA's newcomer of the year for 2008, is enjoying a breakthrough season and has climbed to 12th in the rankings.
"I'm just enjoying every day and every match that I'm playing," said the Dane, whose parents are Polish.
"That I keep winning is just great. I just felt like I was playing really well today. I just got everything together," she told reporters.
Wozniacki will play Svetlana Kuznetsova, who comfortably won her all-Russian fourth round tie with Alisa Kleybanova 6-2 6-1.
Fifth-seed Venus Williams came from a set down to beat Poland's Agnieszka Radwanska 4-6 6-1 6-4 and her sister Serena, the world number one, faces China's Zheng Jie later on Monday.
Hungarian Agnes Szavay, who eliminated Ivanovic, lost 6-2 6-4 to Belarussia's Victoria Azarenka.
Azarenka's quarter-final opponent will be Australian Samantha Stosur whose impressive form continued with a 6-4 6-4 win over France's Amelie Mauresmo.
(Editing by Ed Osmond, To query or comment on this story email email@example.com)