Poland's Caroline Wozniacki, who justified her top seeding at the US Open by defeating former champion Maria Sharapova, insists that she is a much improved player now and potent enough to beat top stars.

Wozniacki, surprise runner-up to Kim Clijsters at last year's Open, held her nerve against the power-hitting Russian to beat her 6-3, 6-4.

"I got a lot of experience from last year and I'm just so happy that I won today and am through to the quarter-finals," The Telegraph quoted Wozniacki, as saying.

"I definitely think I've improved a lot, not only physically, but also I believe in myself more. I believe I can do it. Also I think I can mix up my game a little bit more than I could last year," she added.

Despite being benefited by Sharapova's 36 unforced errors, including nine double faults, Wozniacki said: "It was a really tough match, Maria is a great player so I knew it wasn't going to be easy."

Sharapova, meanwhile, was left lamenting the fact she had failed to seize break opportunities when she should have.

"I felt like I played a couple of good points and then made an easy error, hit a return long or missed a first serve. I didn't feel like I put much pressure on her," Sharapova said.

Wozniacki will now face Dominika Cibulkova in the quarterfinal. (ANI)