The Australian Open has always been a tough nut to crack.
Maybe it's because it's the first major of the year -- right out of the box. Perhaps it's because it's played on an island on the Far Side of the World.
Even in his glory days, Roger Federer managed to win the Australian Open title only four times in seven years, from 2004 to 2010. Andre Agassi won four crowns in nine years, from 1995 to 2003. No. 1 seed Novak Djokovic can do better than that.
A win here a week from Sunday would give the 25-year-old Serb his fourth Aussie title in six years, a monopoly in terms of tennis. He would become the first man in Open era history to win three in a row. Why has it been so difficult?
"That's a good question," Djokovic said before the tournament. "I like playing here because it's after probably five, six, seven weeks of break. So you get time to recover, regroup, recharge your batteries. You come here fresh. You're motivated and inspired to play some good tennis. In my case, [it] has been working well. This is my most successful Grand Slam."
On Friday, Djokovic won his 17th consecutive match in Melbourne. It wasn't easy -- it rarely is against the unorthodox Radek Stepanek -- but Djokovic prevailed 6-4, 6-3, 7-5.
He was nimble and decisive in beating Stepanek for the eighth time in nine matches. In three matches Down Under, Djokovic's serve has yet to be broken. Djokovic actually is a bigger favorite to win the men's title than Serena Williams is to win on the women's side.
Last U.S. man exits
Over the years, though, Wawrinka has been just a little better. On Friday, he was again, when the 25-year-old American lost back-to-back service games -- at the end of the second set and the beginning of the third. Wawrinka, the No. 15 seed from Switzerland (who is sometimes best known as Roger Federer's doubles partner), won 7-6 (6), 7-5, 6-4.
Querrey, the No. 20 seed, has now lost all three of his career matches to Wawrinka and was the last American man to exit the draw.
His third-round departure means he failed to post his best-ever Australian Open effort and is still looking to advance to his first major quarterfinal. Wawrinka, meanwhile, will have to beat No. 1 seed Novak Djokovic to reach his third career Grand Slam singles quarterfinal.
Wawrinka converted his fourth match point with a stylish backhand winner down the line, breaking Querrey for the third time. Their previous major encounter, at the 2011 U.S. Open, went 4 hours, 28 minutes before Wawrinka prevailed in five sets.
Keys to the kingdom
Madison Keys, the 17-year-old American with a big game, had a terrific run in Australia. Three-time major champion Lindsay Davenport, a Tennis Channel analyst in Melbourne, said she believes Keys has the most potential of any American woman since Serena Williams.
Keys made her first WTA-level quarterfinal in Sydney, beating No. 17 Lucie Safarova and No. 42 Zheng Jie in the process. Then, in only her third Grand Slam main draw, she got to the third round before losing Friday to No. 5 seed Angelique Kerber 6-2, 7-5.
It was closer than the score suggests. Keys had two break points against Kerber (celebrating her 25th birthday) to force a second-set tiebreaker but went for too much. Her serve is lethal, already one of the best weapons on the women's side, but her backhand and movement need some work. That will come with experience.
Keys has been itching to play a full-time schedule but has been restricted by WTA rules. That all changes Feb. 17, when she turns 18 and can play an unlimited schedule.
Kvitova Czechs out
When she won the 2011 Wimbledon title at 21, it looked like Petra Kvitova was destined to become a force in women's tennis.
The subsequent first-round loss at the U.S. Open made sense, but she fell in the semifinals of last year's Australian Open and French Open -- to Maria Sharapova on both occasions -- and went out in the quarterfinals at Wimbledon (losing to Serena Williams) and the fourth round of the U.S. Open (to Marion Bartoli).
In this year's Australian Open, it looked like the powerful Czech was regressing. The No. 8 seed fell in the second round to British teenager Laura Robson 2-6, 6-3, 11-9 in a match that carried into Friday morning local time.
The sloppy matchup of big-swinging lefties went three hours, and featured 92 unforced errors and 30 aces. The line that captures Kvitova's all-or-nothing game: 18 aces and 18 double faults. She has lost three of five matches in this new year.
"I never gave up," Robson said afterward. "Even when she went up a break twice in the third, I just thought, 'I can always break her.' In the end I just thought, 'I've got nothing to lose, so I'm just going to relax on my serve a bit more and go for it.'"
Robson, who turns 19 on Monday, plays 19-year-old American Sloane Stephens in a compelling third-round match later Friday. The winner has a terrific chance of reaching her first career Grand Slam quarterfinal.
They know each other well; they've been playing since they were 11 years old, and the No. 25-ranked Stephens beat Robson in her first match of the year in Hobart, Australia, 6-4, 7-6 (4).