Will Sharapova's power reign supreme?

NEW YORK -- What rules in women's tennis at the moment: defense or offense? The women's game has been dominated by powerful hitters who go for the first strike -- from Steffi Graf to Monica Seles to Serena Williams -- but canny, fleet-footed counterpunchers have also thrived when the big guns misfire -- Aranxta Sanchez Vicario, Martina Hingis and Jelena Jankovic.

The latest showdown takes place in the fourth round of the U.S. Open as former champ Maria Sharapova, one of the best offensive players, meets top seed Caroline Wozniacki, one of the best defenders, in a blockbuster Labor Day match.

Wozniacki is on a roll, having won the Rogers Cup in Montreal and the Pilot Pen in New Haven back-to-back leading up to the U.S. Open. But for a top seed at a Grand Slam (albeit only because Serena Williams is not playing), her résumé is relatively modest -- one Grand Slam final, which she reached at Flushing Meadows last year.

But the sunny 20-year-old from Denmark has so far backed up her lofty position, striking the ball crisply and dropping just three games in the first three rounds. Not even the most dominant No. 1s have been that stingy during the first week of a Grand Slam.

"I think I've shown I belong where I am, and I'm just happy to be through to the fourth round," Wozniacki said. "For me, it's just about winning the matches. I think it's up to everyone else to judge what I've shown or not shown."

Wozniacki knows that she will have to counter Sharapova's power with her own stellar defense and try to outmaneuver the Russian. "I need to be ready that she's gonna try to attack from the first ball, and I need to be fast," she said.

A win against Sharapova would help Wozniacki prove that her game is now at a level capable of prevailing against the strongest players and make her a fully fledged Grand Slam threat. Until now, she has had only two top 10 wins this season -- one over Agnieszka Radwanska and the other versus French Open champ Francesca Schiavone. Sharapova is not currently in the top 10 after missing a few months this season with an elbow injury, but her three Grand Slam titles and recent run of form make her a true test for any player.

Although Wozniacki is trying to carve out new territory, former No. 1 Sharapova, 23, is trying to show she has reclaimed lost ground and remains ahead of the younger players coming up. Symbolic evidence of that came in her third-round match on Saturday. She wasn't just beating Beatrice Capra, she was erasing the sting of defeat to last year's American teen queen, Melanie Oudin.

On that day, Sharapova, her shoulder and serve still shaky after surgery the previous fall, lost a tortured three-set affair to a fearless 17-year-old Oudin in Arthur Ashe stadium on the middle Saturday. She served 21 double faults.

This year, Sharapova wiped those memories clean with a 6-0, 6-0 defeat of Capra on the same court. She served 10 unreturnable serves, got a very respectable 67 percent of her first serves in and won 80 percent of those points.

"This was a new day," Sharapova said.

It has been a long road. After undergoing shoulder surgery in October 2008, Sharapova took almost a year to get her serve back to normal levels. "We'd set a date of when I can start hitting the ball and hitting a few serves, and I'd hit forehands and backhands and I was fine. I tried to hit a serve, and I couldn't," she said. "I was still in a lot of pain. That was even after the rehab and after surgery."

Despite all the opponents she's stared down, and the three-setters she's fought through, it's this recovery period that Sharapova sees as her biggest show of mental strength. "Coming back from that and setting another timetable for yourself and doing it over and over again until I slowly found myself working myself up to hitting 10 to 15 serves, 20 serves, and being able to do that without pain and really being patient," she said.

Sharapova has been famed for her toughness and competitive drive ever since winning Wimbledon as a 17-year-old in 2004. But Wozniacki doesn't have any shortcoming in that department either, says Darren Cahill, who has worked with Wozniacki as part of the adidas player-development program.

"She's got that X factor when it comes to competing," he said in an interview last month. "She hates to lose.

"I've always compared her to a young Lleyton Hewitt that gets out there and runs down every single ball, despises losing and would fight tooth and nail to make sure that didn't happen."

A battle of wills and a battle of styles. Whoever wins will become the favorite to reach the final, though tricky opponents like Svetlana Kuznetsova and Vera Zvonareva remain. And perhaps the result will show whether it's a great offense or a great defense that wins the day at the moment.

Kamakshi Tandon is a freelance tennis writer for ESPN.com.