MELBOURNE, Australia - The self-appointed sports capital of Australia got a feast of tennis on a lazy, sun-drenched Saturday afternoon.

While top-seeded and three-time champion Roger Federer played Albert Montanes in a Rod Laver Arena crammed with 15,000 fans, top-ranked and Australian Open defending champion Serena Williams took on Carla Suarez Navarro at the neighbouring show arena with a retractable roof that seats 10,000.

One hour and 48 minutes and 1:21 later, respectively, Federer and Williams walked off their courts after booking fourth-round matches on Monday. Federer beat Montanes 6-3, 6-4, 6-4 and Williams defeated Suarez Navarro 6-0, 6-3.

"I feel good, I feel confident," Federer said. "Pretty straightforward match. Physically I'm fine and mentally fresh and that's the way you want to go into the second week."

Williams, who beat Dinara Safina in last year's final, needed a marathon final game of the opening set Saturday to clinch it, facing five break points, 13 deuces and won on her eighth set point. The final game lasted nearly 20 minutes -- longer than the five previous games combined in the 37-minute set.

By that point, Federer and Montanes were in the fifth game of their second set.

"I think it was definitely the toughest 6-love set, especially in the end because she was really fighting for it," Williams said. "I thought, 'OK, Serena, don't put too much pressure on this. Worst-case scenario it will be 5-1."'

Serena's sister Venus also advanced when she beat Australian wild-card entry Casey Dellacqua 6-1, 7-6 (4), winning on her fourth match point with an ace. The Williams siblings could meet in the semifinals but Venus must first overcome Francesca Schiavone of Italy, who beat Agnieszka Radwanska of Poland 6-2, 6-2.

Venus is thinking final, which would mean beating Serena along the way.

"Of course I want to progress well to the final, that is my goal," Venus said. "So far, I'm getting closer. You know how it works. Just got to play well every match."

Melbourne sports fans regularly pack a 100,000-seat Australian Rules football and cricket stadium and turn the southern hemisphere's biggest horse race -- the Melbourne Cup -- into a weeklong festival.

Australia's top player, former No. 1 Lleyton Hewitt, advanced when 2006 finalist Marcos Baghdatis had to retire with a right shoulder injury with Hewitt leading 6-0, 4-2 in a night match at Rod Laver Arena.

The last time the pair met here, they started just before midnight and concluded the match -- won by Hewitt -- at 4:34 a.m. Hewitt now plays Federer in the fourth round.

This Hewitt-Baghdatis rematch lasted just 54 minutes.

"I just said to him, 'mate you've got a lot of ticker (heart) to come back like you did today,"' Hewitt said he told Baghdatis when the Cypriot player came to the net to retire.

Baghdatis had clutched his shoulder during changeovers and motioned to his coach that he was having difficulty breathing due to the pain.

"I just feel some pain on the shoulder ... I couldn't hit the forehand," Baghdatis said. "I couldn't control the ball. I didn't think that it would be this painful during the match."

In completed men's matches, sixth-seeded Nikolay Davydenko beat Juan Monaco of Argentina 6-0, 6-3, 6-4 and will face Fernando Verdasco in the next round. Verdasco advanced when Stefan Koubek had to retire after losing the opening set 6-1 due to a virus.

No. 3-ranked Novak Djokovic, who beat Federer in the semifinals en route to his 2008 title here, defeated Denis Istomin 6-1, 6-1, 6-2. Earlier, No. 20 Mikhail Youzhny withdrew from his scheduled third-round match against Poland's Lukasz Kubot with a wrist injury. Kubot advanced in a walkover and will play Djokovic.

Frenchman Jo-Wilfried Tsonga, who lost the final to Djokovic in 2008, beat Tommy Haas of Germany 6-4, 3-6, 6-1, 7-5 in a night match. Tsonga will play Nicolas Almagro of Spain, who beat Alejandro Falla of Colombia 6-4, 6-3, 6-4.

In women's matches, U.S. Open runner-up Caroline Wozniacki of Denmark beat Shahar Peer of Israel 6-4, 6-0. Wozniacki will face Li Na of China, who equalled her best run at Melbourne Park when she advanced 7-5, 3-6, 6-2 over 2008 semifinalist Daniela Hantuchova.

Sam Stosur beat Italian Alberta Brianti 6-4, 6-1, No. 7 Victoria Azarenka of Belarus had a 6-0, 6-2 win over Italy's Tathiana Garbin to set up a fourth-rounder against No. 9 Vera Zvonareva of Russia, who beat Argentina's Gisela Dulko 6-1, 7-5.

Stosur will next play Serena Williams. No. 13-seeded Stosur beat the 11-time Grand Slam singles champion the last time they played in California last year.

"I just remember I hit some great shots and she returned them back for winners," Williams said. "I know what to expect. She has nothing to lose going into this match."

Federer has plenty to play for -- he'd like to win his fourth Australian Open title and walk away from Rod Laver Arena on Jan. 31 without tears in his eyes, as he had last year when he lost to Rafael Nadal in the final.

Federer spoke Saturday about his mental toughness, which he said is needed to "stay at the top of the rankings for so long."

"Victories don't come easy," Federer said. "I had to battle through, and there was tough moments and frustrating moments out there. You have to be mentally strong to be at the top no matter, regardless of the player you are."

Federer then spoke about Nadal, who plays his fourth-round match Sunday against Ivo Karlovic.

"With him, it's from point one to the last point it's always the same intensity," Federer said. "He never drops it."