NEW YORK—Caroline Wozniacki, who has endured an injury-plagued season, says she is finally healthy.

"Everything is feeling good,” she said after defeating Monica Niculescu in the third round of the U.S. Open.

Coming into the Open, Wozniacki hadn’t won a Grand Slam match all season.

The 26-year-old has fallen to No. 74 in the rankings following a subpar stretch of play, but she is starting to again resemble a top player.

"I'm not that worried about the ranking at this point,” she said. “I'm just happy to be healthy and back playing. Whether I'm 70 or 30 in the world, it really doesn't matter. If I'm not Top 10 or seeded every tournament, it really doesn't matter. I can beat anyone on a good day."

The former world No. 1 recently changed coaches, and has had to contend with ankle and wrist injuries this season.

"It's been a rough year because I haven't been able to catch a break from injuries," she said. "[I had to] skip the whole clay season, and [was] still not feeling 100 percent going into [the] grass [season] ... I started on the grass thinking, ‘I'm going to get some matches here, and that's going to get me really into the hard-court season, and I will be 100 percent ready for that.’

"So I went into the grass season just trying to get momentum going. Then hurting myself in Washington wasn't really part of the plan."

She entered the tournament with just five wins in her last 12 matches. But three victories later, she’s into the fourth round of the U.S. Open and will play Madison Keys for a spot in the quarterfinals.