The winning run of unseeded 17 year old American Melanie Oudin has come to an end at the U.S. Tennis Open, beaten in straight sets by Danish teenager and ninth seed Caroline Wozniacki.
Wozniacki won 6-2, 6-2, to advance to the semis with Oudin disappointed not to have pushed her given she eliminated Olympic champion, former champion Maria Sharapova and 13th seed Nadia Petrova in previous rounds.
The women's semi finalists are now decided with Wosniacki playing the unseeded Belgian Yanina Wickmayer while defending champion Serena Williams plays Kim Clijsters, back after taking two years off to start a family.
Meanwhile the fives times champion Roger Federer's weathered a strong comeback from Sweden's Robin Soderling to advance to the semi-finals.
Federer looked as if he was hardly going to raise a sweat when he polished off the first set six love, and then took the second 6-3.
But Soderling came back in the third which he took 7-6 in a tiebreaker.
The fourth also went to the tiebreak, but in Federer's favour, taking the match which didn't finish till after midnight, in four sets.
Soderling's now lost all twelve of his encounters with Federer, who plays fourth seed Novak Djokovic for a place in the final.