WIMBLEDON, England (AP) — As the 125th edition of Wimbledon heads into its second week, all of the principal story lines are still there to be followed.
Roger Federer has yet to drop a set as he bids for a record-tying seventh championship. Rafael Nadal hasn't lost a set, either — the first time he's done that through three rounds — as he aims for a third Wimbledon title and 11th major trophy overall.
Novak Djokovic and Andy Murray are around, too. Murray hopes to give Britain its first male champion at the All England Club since 1936.
And then there are the Williams sisters, whose comebacks are producing win after win so far. They have combined to win nine of the past 11 Wimbledon singles championships, and while Serena was sidelined for nearly a year with a series of health scares, and Venus missed about five months with a hip injury, both are clearly capable of producing top-level tennis at the grass-court Grand Slam tournament.
"Yeah, I'm still alive, and it feels good," said Serena Williams, who could become the first woman since Steffi Graf in 1991-93 to win Wimbledon three years in a row. "You know, I'm hoping to be around — and planning to be around — a lot longer."
Also in the picture are top-seeded Caroline Wozniacki, hoping for her first Grand Slam title, and 2004 Wimbledon champion Maria Sharapova.
After Sunday's traditional day off, action resumes Monday with all 16 men's and women's fourth-round matches.
Two stand out in particular. Top-seeded Nadal takes on No. 24 Juan Martin del Potro of Argentina, while No. 23 Venus Williams faces No. 32 Tsvetana Pironkova of Bulgaria in a rematch of the 2010 Wimbledon quarterfinal won by Pironkova.
Nadal slipped behind the baseline a couple of times during his third-round victory over Gilles Muller, and afterward, the Spaniard acknowledged he was bothered by a right leg muscle. But he also said he can "play with that, without problems."
After so many years of dominance on clay — he won his sixth French Open championship this month — Nadal has become quite good on grass. Since the start of Wimbledon in 2006, he is 29-2 at the tournament. His only losses were to Federer in the 2006 and 2007 finals; Nadal won the 2008 and 2010 titles, and was sidelined in 2009 by tendinitis in his knees.
"Against him, you should play unbelievable tennis. You should play everything perfect, and then maybe you have a little chance," del Potro said. "He will be the big favorite."
Well, that might be true. But even though del Potro lost in the second round in all three previous visits to the All England Club, his chances against Nadal shouldn't be dismissed entirely.
After all, at the 2009 U.S. Open, del Potro did beat Nadal in the semifinals, then Federer in the final — the only time someone beat both Nadal and Federer in the course of a single Grand Slam tournament. It's also the only time in the past 25 major tournaments that a man other than Federer, Nadal or Djokovic took the title.
Del Potro is working his way back into form after missing most of the 2010 season because of surgery on his right wrist, and while he's seeded 24th, Nadal pointed out that "his ranking, for sure, is much better than what the ranking says today. His level is much better than what the ranking says today."
The top four of Nadal, No. 2 Djokovic, No. 3 Federer and No. 4 Murray filled out the semifinals at the French Open, and no one would be too surprised if they did that again at Wimbledon.
For Federer, who plays No. 18 Mikhail Youzhny on Monday, it's been about 1½ years since he won a Grand Slam title; his 16th came at the 2010 Australian Open.
"I don't go through days thinking, like, 'My God, I haven't won a Grand Slam in so long.' It hasn't been that long, to be honest," said Federer, whose six Wimbledon titles are one behind Willie Renshaw (who played in the 1800s) and Pete Sampras.
"I'm always hungry," Federer added. "And that's a good thing."
Djokovic, whose 43-match winning streak ended with a loss to Federer in the French Open semifinals, takes on No. 19 Michael Llodra, at 31 the oldest man left and finally in the fourth round on his 11th appearance at Wimbledon.
Two-time semifinalist Murray faces No. 17 Richard Gasquet, while the last American man in the field, No. 10 Mardy Fish, plays 2010 runner-up Tomas Berdych.
Women's matchups include No. 7 Serena Williams against No. 9 Marion Bartoli, the 2007 runner-up; Wozniacki vs. No. 24 Dominika Cibulkova; and No. 5 Sharapova vs. No. 20 Peng Shuai of China.
Venus Williams' straight-set loss against Pironkova a year ago represented only the third time in the American's past 11 trips to Wimbledon that she didn't reach the final.
"Unfortunately, I didn't play that well. On a competitive level, I don't feel I competed well. Regardless of how I play, I know I'll be competing this time," said the older Williams sister, who has won five of her seven career Grand Slam singles titles at the All England Club.
"Last year, I let a few games get away, and instead of coming back, I let it all get to me. You can't do that, especially in a Wimbledon quarterfinal," she continued. "I won't let anything get to me this time."