NEW YORK — The U.S. Open begins Monday with restored star power, a year after the women’s draw had just one Grand Slam champion among its top five seeds and three of the top five men in the world rankings missed the event because of injuries.

Now Serena Williams, a year after giving birth, is lurking at the 17th seed while the top four seeds — Simona Halep, Caroline Wozniacki, Sloane Stephens and Angelique Kerber — are the reigning singles champions for each Grand Slam tournament. In the men’s draw, Rafael Nadal, Roger Federer and Novak Djokovic (who could not play last year) will each be seeking his second Grand Slam title of 2018.

But this could also be the year for one of these outsiders at Flushing Meadows.

Caroline Garcia

At 17, Garcia led Maria Sharapova, 6-3, 4-1, in the second round of the 2011 French Open, and Andy Murray said on Twitter: “The girl Sharapova is playing is going to be number one in the world one day. Caroline Garcia, what a player.” Garcia, 24, lost that match and has been plagued by inconsistency — a talented shotmaker who would score the big upset then falter in the next round. But she gained confidence on the doubles court, working primarily with fellow Frenchwoman Kristina Mladenovic. They won the French Open doubles in 2016, and Garcia decided to focus solely on singles the following year. She achieved her best Grand Slam result in 2017, reaching the quarterfinals of the French Open. Now ranked sixth in the world, she will arrive in New York fresh off a strong showing at the Connecticut Open. With power off both sides, pinpoint serving and superb athleticism, Garcia is an aggressive baseliner who can finish at the net. Her decision making and shot tolerance have greatly improved, and she can transform a rally with a dazzling winner.

Kiki Bertens

Bertens, a powerful 26-year-old from the Netherlands, has had a stellar summer. Before she reached the quarterfinals at Wimbledon, Bertens was 0-11 against top 10 opponents, but since then she has won eight straight matches against top 10 players. In Cincinnati last week, the 6-foot Bertens had her finest career showing, toppling Coco Vandeweghe, Caroline Wozniacki, Anett Kontaveit, Elina Svitolina, Petra Kvitova and, in the finals, top-ranked Simona Halep. Bertens, ranked 13th, attributes her turnaround to a renewed commitment to practice and fitness. Although her signature groundstroke is her inside-out forehand, Bertens can hit punishing shots off either wing. With improved speed and stamina, she is able to stay in points longer, forcing errors rather than going for winners because of fatigue. Her victory in Cincinnati was an example of the growing depth in the women’s game.

Aryna Sabalenka

Sabalenka, along with Aliaksandra Sasnovich, led Belarus to its first Fed Cup final in 2017, and she has had a successful North American hardcourt season this year. She had a breakout tournament in Cincinnati last week, vaulting to No. 25 in the WTA rankings with wins over Johanna Konta, Karolina Pliskova, Caroline Garcia and Madison Keys before falling to No. 1 Simona Halep in the semifinals. Sabalenka, who is 6 feet tall, hits with blistering pace off both sides, and she is capable of hitting a winner from anywhere on court. In January, she hired Magnus Tideman, the Swedish veteran who has coached Jeremy Chardy and Thomas Johansson. Tideman has helped Sabalenka, 20, improve her patience and shot selection. Like Victoria Azarenka and Maria Sharapova, Sabalenka is often criticized for loud grunting as she strikes the ball. But with her fearsome ball striking and competitiveness, Sabalenka is capable of making a deep run.

Stefanos Tsitsipas

A year ago, Stefanos Tsitsipas of Greece was ranked 168th and had yet to win a match on the main tour. He moved up to No. 15 in the world this month as he defeated Dominic Thiem, Novak Djokovic, Alexander Zverev and Kevin Anderson on his way to the final at the Rogers Cup in Toronto, where on his 20th birthday he lost in straight sets to Rafael Nadal. At 6-foot-4, the lithe, angular Tsitsipas has a powerful first serve, a nearly perfect one-handed backhand and a lethal forehand that he hits with pace and disguise. But what truly makes Tsitsipas a delight to watch is his movement. His ability to slide on hard courts and improvise on defense call to mind Nadal and Djokovic, and when he attacks the net, his graceful athleticism is reminiscent of Roger Federer. Last year Tsitsipas lost in the final round of qualifying at Flushing Meadows, but he comes to New York as the 15th seed and brimming with confidence, a future Grand Slam winner on the threshold of tennis greatness.

Frances Tiafoe

Tiafoe, 20, became the youngest American to win an ATP Tour title since Andy Roddick in 2002 when he captured the Delray Beach title in February. Coached by Robby Ginepri, who lost an epic five-set match in the 2005 U.S. Open semifinals against Andre Agassi, Tiafoe has made a steady ascent to No. 42 in the rankings. With his punishing two-handed backhand and dominating serve, Tiafoe came close to upsetting Roger Federer in the first round at Flushing Meadows a year ago, losing in five sets. But Tiafoe’s forehand, long the weakness of his game, broke down against Federer. With Ginepri’s guidance, Tiafoe has improved the forehand to the point where it is a weapon rather than a weakness. In a recent win over Milos Raonic in Toronto, Tiafoe was rock solid from the baseline, returning Raonic’s huge first serve and using his superb speed to take over the match. Tiafoe thrives in a big match atmosphere, and he is capable of making a deep run in front of a boisterous, partisan crowd.

Milos Raonic

With the arrival of two fellow Canadians — Denis Shapovalov, a sublimely gifted 19-year-old, and Felix Auger-Aliassime, who at 18 is less heralded but equally talented — Raonic, 27, has stepped up his game. He defeated Shapovalov in straight sets in Cincinnati this month before losing a tight three-setter to Novak Djokovic, the eventual champion. Although the 6-foot-5 Raonic has one of the game’s best serves, he has struggled with his movement and his ability to change tactics. Goran Ivanisevic, his coach, has helped him become more nimble and agile in his court coverage. Raonic now volleys with greater feel and accuracy. His defense, once nonexistent, has become stingy under Ivanisevic’s watchful eye. Against Shapovalov, Raonic tracked down several fearsome forehands, using chips and dipping passing shots to frustrate his young opponent. The battleground for Raonic, who is ranked 25th, will be his ability to win points on his second serve. Against Djokovic — arguably the game’s best returner — Raonic won only 40 percent of second-serve points. If he can get closer to 50 percent in that category, Raonic could be a true contender.