Serena sees off stubborn Vaidisova

MELBOURNE (Reuters) - Champion Serena Williams applied the pressure when she need to and withstood a tough fourth-round challenge from Nicole Vaidisova on Sunday to reach the Australian Open quarter-finals.

The American seventh seed won the match 6-3 6-4 after being forced to dig deep in the second set when her 12th-seeded Czech opponent attempted to force a decider.

However, just as the rangy Vaidisova looked to capitalize on a second set break of serve, the American broke immediately back to go ahead 5-4 with the opportunity to serve for the match.

The 18-year-old Vaidisova, who smashed her racket on the court at the end of that game, was seen talking to herself constantly during the changeovers.

Williams then capitalized on the teenager's frustration and served to love to seal victory.

"I think I had my chances, especially in the second set," Vaidisova told reporters. "Didn't choose the right shot, maybe went for too much. She pushes you to do that.

"That was the difference. The points that were very important, she went out there and played a great point."

Williams, who beat Vaidisova in the semi-finals at Melbourne Park last year, said she believed her opponent had a big future.

"It's definitely interesting playing her," said Williams.

"She's so unpredictable. I think that's really a good thing.

"Last couple of times I played her, her serve has just been really, really, really good."

Williams will face either third-seeded Serbian Jelena Jankovic or Australia's Casey Dellacqua in the last eight.

"At the end of the day, I never really get upset at whoever I play because I'm totally fine.

"As long as I'm not playing Venus in the quarters, it doesn't matter to me.

"Eventually you're going to have to play everyone else."

(Editing by Ed Osmond)