As the world's No. 8 tennis player, Caroline Wozniacki sounds like she will make a good first-time marathon runner.

"To learn to run and drink at the same time," she said, "has been a little bit of a challenge. I usually am sitting down. So that's going to be interesting. To run and drink at the same times, it goes all over the place."

As an elite athlete, who works out or plays tennis "three or four hours every day," she figures she is off to "a pretty good start" to take on Sunday's New York City Marathon.

Except she never has run a race before, much less one of 26.2 miles. "I'm a little nervous," she said. "I had dreams at night where I didn't finish and had to be carried through with a wheelchair. But I did a half [marathon] and felt great. And I thought, 'You know what? It's OK. I can finish it.' "

The idea of taking on the marathon in the midst of her athletic career -- something only a handful of top professionals have tried, and then only after retirement from their sports -- struck Wozniacki during a dinner before June's Wimbledon championships.

She was planning her schedule for the rest of the year, and the New York City Marathon "always was on my bucket list." The Nov. 2 date fell exactly a week after the conclusion of the tennis season -- she just arrived from the Singapore finals Tuesday night -- "and I always take three weeks off after the season, where I never touch a racket. I thought: Why not start off my vacation by running a marathon?

"Everyone was, like, 'No way; you're not. You're crazy.' Right then and there, I called my manager, John Tobias: 'Can you look up charities that I can run for?' "

From Tobias' list, she picked the Team for Kids organization, which has raised more than $4.5 million to support youth fitness programs. Wozniacki already has procured donations of $50,000, some of it from fellow tennis pros such as Andy Murray, and from the Women's Tennis Association.

"Serena," Wozniacki said, "you're still missing."

She has "no routine" running schedule, Wozniacki said. In the evenings, after morning tennis matches. In the mornings, if she is scheduled to play at night. Sometimes she runs for 30 or 40 minutes, sometimes for an hour and a half, but she found running "clears your head. You become so happy. And you can eat more, which is a great thing."

Days after this past summer's U.S. Open, she was running in Central Park when fellow runners were "stopping and clapping and giving the thumb's up," she said. "That was so cool."

She expects plenty of friends in town for support Sunday, though "my parents bailed on me," she said. "They said, 'We're going on holiday. Enjoy yourself. You're going to be fine.' "

She will be running with two Team for Kids volunteers. "Hopefully," she kidded, "they can keep up."