MELBOURNE, Australia - Maria Sharapova emerged victorious in a battle of former World No.1s on Friday, ending Caroline Wozniacki's title defense, 6-4, 4-6, 6-3, to reach the fourth round of the Australian Open.

Champion in Melbourne back in 2008, Sharapova fell in the third round to a surging Angelique Kerber last year; facing another big name in the Round of 32, the Russian used all of her firepower to break through the Dane's signature defense and secure the win after two hours and 24 minutes on Rod Laver Arena.

"As usual, it was a physical match," Sharapova said. "It was a good win. I'm just really happy and proud of the way I competed today."

Both women enjoyed strong starts to their Australian Open campaigns - neither had dropped a set while Sharapova lost just three games in two matches - but it was Wozniacki who settled sooner to start the match, taking a 4-1 lead.

Sharapova came to life from there, rolling through the next five games with the help of 16 winners to just five from the defending champion.

"In my mind, it didn't feel like was 1-4," she said. "I challenged her from the very beginning. I had three break points in the first game. Although I didn't take them, I felt like I was still putting the pressure on."

While Wozniacki would hit just one winner in the second set, she confounded Sharapova into 19 unforced errors as she worked to level the match after moving ahead 3-0 to start. The Russian netted a forehand dropshot in the ninth game that helped Wozniacki hold and ultimately break to force a decider.

The final set was as tense as any played throughout their 11-match rivalry; Sharapova had won their most recent meeting at the 2015 Mutua Madrid Open, but Wozniacki claimed the edge on hardcourts, winning back-to-back three-setters at the 2014 US Open and BNP Paribas WTA Finals Singapore presented by SC Global.

Trading service holds through the first six games, Sharapova came to break point first as Wozniacki served down 15-40. Though the Dane would save both, she couldn't shake Sharapova, who let out a roar as she edged ahead what would be a crucial break.

With a calm love hold, Sharapova earned a match point at 5-3, but couldn't convert after a long rally. A strong return set up a second match point and Sharapova ultimately overpowered her rival for a dramatic win.

"It just wasn't enough today," the 2018 champion said. "I did my best. I did all I could, I just came up short. That's sport sometimes.

"I thought from the middle of the second set, we both picked it up. And I think in the third set we both played well."

In all, the Russian took more risks with 37 winners to 46 unforced errors, but it was her solid serving that truly won the day for the five-time major champion, maintaining a 62% first serve percentage and winning 74% of those points overall. Typically a strong returner, Wozniacki will rue her 22% of points won against the Sharapova serve, ending the match with 10 winners to 21 unforced errors.

"I felt that even in the longer rallies, I did a great job of winning those and put a lot of pressure on her," Sharapova said. "Those are the rallies that many years ago she used to win. I thought I did a great job of getting a high percentage of wins in those.

"Getting into long rallies with her isn't ideal - she lives off that type of tennis. 

"So I wanted to be the one who's forcing the mistakes. In a match like that against a player that moves well, I'm not necessarily expecting to hit winners left and right, even if that would be nice - free points feel good - but that's not what you have to expect."

Wozniacki, meanwhile, reflected on what she felt was an enjoyable defense of her crown.

"I found it kind of pleasurable, it was nice and exciting, and I think it was great," she said. 

"You know, in tennis, you're one on one, and you battle and you do your best. One day you win; some days you lose.

"As long as you give it your all out there, as long as I fought for every point and was really trying to do everything in my power to win, I can't really blame myself for anything."

Up next for Sharapova is Aussie No.1 and No.15 seed Ashleigh Barty, who began Day 5 with a career-best result at her home major, defeating Greek youngster Maria Sakkari, 7-5, 6-1.