No one questioned whether Wozniacki was a world-class athlete. Ranked eighth in women’s tennis, she needed only to prove to the world, and especially herself, she could run 26.2 miles.

Boston? Yeah, her time was that good.

On a cold, windy day in New York, with 50,000 other competitors and celebrities, Wozniacki completed the longest run of her life in 3:26:33. For the record, that’s a great time for a novice, ranking along just under eight minutes per mile.

“I thought I was gonna die,” Wozniacki said.

Her race run, Wozniacki was greeted at the finish line by pal Serena Williams, who was bursting with pride.

Williams also put images in Instagram.

According to USA Today, Wozniacki felt great after 13 miles, deciding to try to beat a pedestrian four-hour time. Then she hit the wall after 20 miles.

A video posted by Serena Williams (@serenawilliams) on Nov 11, 2014 at 10:26am PST

“I’ve never tried anything this hard,” Wozniacki said. “This was the toughest physical test I’ve ever (had). It’s so hard. You have to keep going, keep going. Once I got onto First Avenue, I had a camera crew following me the whole day, so I couldn’t walk. I had to keep running.”

As for her prerace regimen, Wozniacki admitted to staying up late and on Saturday night eating popcorn at a hockey game, NBC Sports reported. “I’ve done everything you’re not supposed to do before a marathon,” she said.

Wozniacki was a winner, beating her limitations and proving being “a little crazy, but in a good way” can carry anyone to personal triumph.

Team for Kids, a charity that funds local and national fitness programs, also was a winner. Wozniacki’s run put money in its coffers.

“Right now, I’m tired, so exhausted,” Wozniacki told USA Today. “But I’m sure I’ll look back on this experience and think it was awesome and want to do it again.”

How did her run stack up against other celebs?

Consider this list of former tennis players in past yeas from NBC Sports: Amelie Mauresmo, 3:40:20; Yannick Noah: 4:01:38; Justin Gimelstob: 4:09:58.

Bill Demong, a 2010 Olympic champion in Nordic combined, reportedly finished Sunday’s run in 2:33:05.

“I never tried anything this hard,” Wozniacki said after the race. “This is the toughest physical challenge ever. You have to keep going, keep going. I just kept grinding out there.”