NEW YORK >> Four times, 2014 U.S. Open runner-up Caroline Wozniacki was one point from winning. Four times, her opponent in the second round, 149th-ranked Petra Cetkovska of the Czech Republic, came up with a winner to extend the match.

The fourth-seeded Wozniacki failed to convert any of those four match points and lost 6-4, 5-7, 7-6 (1) to Cetkovska, who had not won a tour-level main-draw match all season until this week.

Wozniacki held one match point while ahead 5-4 in the third set, then three more at 6-5.

"I said, ‘It’s now or never,’" Cetkovska said, "so I just went for it."

It was a back-and-forth match that began under the lights and see-sawed wildly for 3 hours, 2 minutes, until it finished after midnight as Thursday turned to Friday. The women combined for 12 breaks of serve.

Wozniacki has made it all the way to the final at Flushing Meadows twice, losing to Serena Willams last year and to Kim Clijsters in 2009.

Her exit means only three of the top 10 seeded women are left after two rounds: No. 1 Williams, No. 2 Simona Halep, and No. 5 Petra Kvitova.

Wozniacki won the first three games and led 4-2 at the start. Then Cetkovska won seven games in a row to take the opening set and lead by two breaks in the second.

But Wozniacki made her way back into it, helped by Cetkovska’s seeming inability to play well with the lead.

Maybe that’s because she doesn’t have a whole lot of experience winning lately.

She arrived at Flushing Meadows with an 0-5 record this year, until beating Christina McHale of the United States in the first round Tuesday. A left hip injury forced Cetkovska off the tour for about seven months at the end of 2014 and the beginning of 2015, and she was able to get into the field in New York thanks to a rule that protects players’ rankings if they miss time because of injury or illness.

"I was so happy to be able to be back and to compete. And this happens tonight, in front of all of you," Cetkovska told the spectators in Arthur Ashe Stadium. "It’s amazing for me."