Zvonareva wary of Wozniacki threat

Vera Zvonareva believes players are still making the mistake of underestimating Caroline Wozniacki - a mistake she intends not to repeat in today's US Open semi-finals.

Wozniacki is the top seed at Flushing Meadows and the world number two, but critics feel that ranking is "soft" due to a lack of wins against fellow top players.

The 20-year-old Dane has never won a match against either of her potential final opponents in New York, Venus Williams holding a 4-0 head-to-head record against her and Kim Clijsters winning their only previous meeting in the final here 12 months ago.

But Wozniacki has dropped just 17 games in reaching the semi-finals - the fewest since Serena Williams lost 14 in 2002 - and is on a 13-match winning streak with a record of 19-1 since Wimbledon.

And Zvonareva knows from recent experience just how well Wozniacki is playing having lost to her in the final in Montreal last month.

"I think Caroline's got enough experience right now," the seventh seed said. "She's very mature for her age and I think a lot of people are underestimating her. She's going out there and she's doing her job very, very well.

"In Montreal I think I just couldn't find my game. I think I had to play Victoria (Azarenka) in the morning (due to a weather delay) and they have absolutely different styles of game, Victoria and Caroline.

"It was very difficult for me just to change the mindset and switch to another match."

The day's second semi-final sees defending champion Clijsters take on two-time champion Venus Williams, with the pair locked at 6-6 from 12 previous contests.

However, Clijsters has won the last four in succession, including a 6-2 6-1 victory in Miami this year and a 6-0 0-6 6-4 win in the fourth round here last year.

The Belgian is on a 19-match winning streak at Flushing Meadows, having won the title in 2005 and not playing here until winning it again in 2009.

Williams admitted: "She's obviously a great competitor. She plays her best tennis, it seems, at this tournament. I'm sure it's a place she feels really comfortable.

"In coming back from her lay-off, I think she never lost that ability to compete. Obviously she's a very good athlete. When you're a really, really incredible athlete, it really takes your game to another level."

Williams won back-to-back titles in New York in 2000 and 2001 and reached the final the following year, but has not been back to the final since.

"I've always played pretty well here," she added. "I feel really comfortable here and it's great to come back to a place where I have won and a place where I've played well."