NEW YORK—The sound of squeaking sneakers signaled the depths of Ana Ivanovic’s desire. Muted in majors in suffering three first-round exits in her last five Grand Slam appearances, Ivanovic returned to Arthur Ashe Stadium determined to make some noise this Saturday night.

Though she seldom spoke during tonight’s showdown with talented teen Sloane Stephens, the 16th-seeded Serbian’s feet just wouldn’t shut up. Taking the small preparation steps to set up her favored forehand, Ivanovic subdued Stephens 6-3, 6-4, to reach the fourth round of the U.S. Open for the second straight year.

Current world No. 1 Caroline Wozniacki opened the day’s play on Ashe and former No. 1 Ivanovic closed women’s play in dispatching the 106th-ranked Stephens, who may well be the most promising prospect of all the young Americans. The bookend appearances were a revealing reminder that while their career paths have taken different tracks, Wozniacki and Ivanovic cross paths in that each has what the other lacks: 2008 Roland Garros champ Ivanovic owns the major missing from Wozniacki’s trophy collection, while the blond Dane, in her 46th week as No. 1, has sustained the consistent longevity at the top that eluded Ivanovic.

Since dismissing Dinara Safina to rule Roland Garros, Ivanovic has played 14 majors and failed to surpass the third round in 10 of them. Working with new coach Nigel Sears and reuniting with fitness trainer Scott Byrnes, who was in her box when she peaked in Paris, Ivanovic looked fit, played fast and showed plenty of positive body language in breaking Stephens' serve in succession to seize a 3-1 lead. Thumping an ace down the middle, Ivanovic whipped a pair of forehand winners to consolidate for 4-1.

The 18-year-old was excited to make her Ashe debut, but in the early stages the occasion got the best of her, making the fast-footed Stephens look like she was playing on fly paper—she was reactive rather than proactive with her feet. When Stephens double faulted to drop into a 1-5 hole, a quick exit appeared inevitable.

There's an alluring fragility to Ivanovic, who often looks like she wants so badly to do the right thing that she’s more prone to a confidence crisis when things go wrong. She very nearly went off the rails as Stephens broke back, held at 15 for 3-5, then earned triple break point to get back on serve. Successive Stephens errors erased the first two break points, and Ivanovic banged a searing serve down the T to draw even at deuce before closing the first set in 31 minutes.

Coach Roger Smith is working with Stephens on making her formidable forehand even more effective by finishing points at net. It's a play former U.S. Open doubles finalist and singles standout Chanda Rubin used so successfully in exerting her explosive forehand. Stephens says she's planning to buy her first car after the Open ends and she's still learning to negotiate the learning curve: She played predictable patterns on her serve, hitting an overwhelming majority of her serves down the middle on the ad side; she was often forced to hit off her back foot. But the second set showed why Stephens is a player to watch, as she fought back from an 0-2 deficit to collect a 3-2 lead.

Ranging from explosive to erratic, Stephens followed an ace with her sixth double fault to face break point in the ninth game, then lifted a drive beyond the baseline as Ivanovic pumped her fist to celebrate her second straight break and a 5-4 lead. She squealed in delight in wrapping up the win and knows she'll have to play a much more consistent match if she is to test 13-time Grand Slam champ Serena Williams in the fourth round.

"It's gonna be a tough match, she's in great form," said a smiling Ivanovic, who's winless in two prior matches with Serena.

—Richard Pagliaro