MELBOURNE, Australia (AP) — Nearly a week into the Australian Open, the only major surprise is that there have been, well, not many surprises at all.
The year's first Grand Slam is historically fraught with injury withdrawals or top players not yet up to speed in the new season and losing in the first few rounds.
But with the third round complete for the leading players at Melbourne Park, only one of the first eight men's seeds did not advance: No. 6 Juan Martin del Potro. Six of the eight top women were through.
Second-seeded Roger Federer was the last of the main contenders to advance to the fourth round, beating Australian Bernard Tomic 6-4, 7-6 (5), 6-1. Federer trailed 4-1 in the tiebreaker but rallied for six of the next seven points in front of a full house at the 15,000-seat Rod Laver Arena.
"I had a few more chances than he did, but I thought the tiebreaker was going to go his way," said Federer. "I think overall we played a great match, he really got the best out of me tonight."
The four-time Australian Open champion will next play big-serving Canadian Milos Raonic, who beat No. 17 Philipp Kohlschreiber of Germany 7-6 (4), 6-3, 6-4.
Del Potro was a 6-3, 6-3, 6-7 (3), 3-6, 6-3 loser to France's Jeremy Chardy earlier Saturday in the biggest upset so far in this tournament.
Those still around have advanced fairly impressively.
Top-seeded Novak Djokovic and No. 3 Andy Murray haven't dropped a set in three matches, although Murray had his difficult moments in Saturday's 6-3, 6-4, 7-5 win over Lithuanian qualifier and sometimes hitting partner Ricardas Berankis, while fourth-seeded David Ferrer has lost just one set.
"I was struggling, he was making me feel pretty uncomfortable on the court," Murray said.
Chardy broke 2009 U.S. Open champion del Potro's serve in the final set to go up 5-3, then served out the match in 3 hours, 45 minutes.
"I played some tennis I never would have thought I was capable of playing," Chardy said.
Seventh-seeded Jo-Wilfried Tsonga beat Slovenian Blaz Kavcic 6-2, 6-1, 6-4 and will meet countryman Richard Gasquet, who beat Croatian Ivan Dodig 4-6, 6-3, 7-6 (2), 6-0.
Andrea Seppi of Italy beat Croatia's Marin Cilic 6-7 (2), 6-3, 2-6, 6-4, 6-2 to also advance to the fourth round.
In women's play, top-seeded Victoria Azarenka had her problems against injury-affected American Jamie Hampton and needed three sets to advance on Saturday, but No. 3 Serena Williams has not dropped a set despite an injured right ankle.
"There's always two ways — your opponent plays good and you can also make your opponent look good," Azarenka said after her 6-4, 4-6. 6-2 win.
Williams, aiming for a third consecutive major title, recovered from a break down in the second set to win six straight games and beat Japan's Ayumi Morita 6-1, 6-3. She later combined with older sister Venus to win a second-round doubles match.
Williams surprised herself with another serve at 128 mph in an afternoon match in Rod Laver Arena, matching a career best that she hit earlier in the tournament.
"I tried to hit it really hard. I hit 207 (kph) the other day and I thought it was luck," she said. "But I did it again and I was like, 'Whew! I'm going to try to go for 210.' We'll see."
The other half of the women's draw, which didn't play Saturday, is more impressive: No. 2 Maria Sharapova dropped only four games in three rounds — including consecutive 6-0, 6-0 wins to start her tournament, while No. 4 Agnieszka Radwanska is on a 12-match winning streak after capturing tournaments in Auckland and Sydney ahead of her three wins here.
Azarenka appeared frustrated at times, but overcame an early break and fended off triple break point in the seventh game of the deciding set before clinching the match in 2 hours, 9 minutes.
Hampton needed a medical timeout for a lower back problem before she served out the second set. She winced in pain, frequently on the verge of tears, throughout the third but still managed 41 winners to keep the Belarusian under pressure.
"She played incredible, went for every single shot. I felt it was touching every single line," Azarenka said. "She took a medical timeout but she rips winners all over the place and I was like, 'Can I have a back problem?' I'm feeling great, but I'm missing every shot."
After wasting two set points on Azarenka's serve late in the second set, Hampton had to leave the court for nine minutes to have treatment on her back.
Even with the pain of two herniated disks, the 23-year-old Hampton went down swinging — making 47 unforced errors to go with the winners that caught Azarenka off guard and had her asking, loudly at one point, what she could do to counter them.
If results go according to rankings, Azarenka and Williams will meet in the semifinals. Williams has won the Australian Open five times and is on a 19-match winning streak — and she has lost only one match since her first-round exit at the French Open last year.
Considering Azarenka has lost 11 of their 12 meetings, including all five in 2012, it's a potential matchup where Azarenka will have to play better than ever. But they both have to advance to the last four, something Williams failed to do here last year when she was knocked out in the fourth round.
In this year's fourth round, the 31-year-old American will meet No. 14 Maria Kirilenko, who beat No. 20 Yanina Wickmayer 7-6 (4), 6-3. Azarenka next plays Elena Vesnina, who beat 16th-seeded Roberta Vinci of Italy 7-6 (4), 6-4.
Two-time major winner Svetlana Kuznetsova advanced with a 6-2, 4-6, 6-3 win over Spain's Carla Suarez Navarro and will next play former No. 1 Caroline Wozniacki, who had a 6-4, 6-3 win over Lesia Tsurenko.
Sloane Stephens beat Laura Robson 7-5, 6-3 in a matchup between the only teenagers left in the women's draw.