Wozniacki books a showdown against Serena

World number one Caroline Wozniacki said her quarter-final appearance out on Flushing Meadows' modest court 13 on Thursday took her back to her junior days.

But her 6-1, 7-6 (7/5) victory over determined German Andrea Petkovic lined up a semi-final clash with Serena Williams that is anything but small-time.

Wozniacki and Petkovic were pushed out to court 13 because of water seeping to the surface of the Louis Armstrong Stadium court, which was water-logged after days of heavy rain.

"It actually reminded me of juniors," Wozniacki said of the small court with bleacher seating and shade trees, where Petkovic had an enthusiastic following.

However, she didn't feel slighted not to be on Armstrong or the main Arthur Ashe Stadium.

"Well, Andy Roddick was playing on court 13 as well. I heard somebody say the last nine years he hasn't been playing on any other courts than (Ashe). If he's not complaining, I'm not complaining either."

Wozniacki, seeking a first Grand Slam title to back up her number one ranking, will be back in the brightest spotlight the US Open can offer when she takes on 13-time major winner Williams in the semi-finals, which have been pushed back from Friday to Saturday night because of the rain delays, with the women's final now slated for Sunday.

"She's playing great," Wozniacki said of Williams, who missed a year with various health concerns but has roared back this summer with two tournament titles.

"I think she's in great shape. She's been proving that she's back on fire. I'm excited to be out there and play, and hopefully it will be a good match."

Wozniacki, whose runner-up finish at Flushing Meadows in 2009 remains her best Grand Slam finish, survived a hiccup while serving for the match at 5-3 against Petkovic.

She dropped that game and her next service game before putting it away in the tiebreaker.

After playing Wozniacki, Petkovic said she thought the Dane had a chance to beat Williams, even though she lacks a powerful serve or other weapon with which to challenge the American.

"If Caroline plays really well and changes up the rhythm and plays as consistent as she always is, she has chances," Petkovic said.

"I think Caroline is one of the most underestimated players out there, because you have to win each and every point against her. If you don't do it, you lose."

Williams herself said much the same.

"I think her weapon is the fact that she never gives up," Williams said. "That's probably the biggest weapon I think you can have in all of tennis."