WIMBLEDON,  England -- Mardy Fish has gone where he never has before and in this Wimbledon where no other  American male has gone -- the fourth round.

Fish, who at 29 seems to be fulfilling the promise he had at 19, advanced
Saturday when his opponent Robin Haase of the  Netherlands retired with a sore knee after trailing, 6-3, 6-7 (5), 6-2, 1-1.

Serena Williams,  back in competition following a near yearlong absence
following a cut foot,  pulmonary thrombosis and a hematoma, looked her best so far, cruising past Maria Kirilenko of  Russia, 6-3, 6-2.

On a warm, sunny afternoon, a contrast to the rain which postponed a great deal of play Friday, it was a tournament for favorites. Defending champion and top seed Rafael Nadal,  No. 2 seed Novak  Djokovic and six-time winner Roger Federer all  advanced. Bernard Tomic, 18, became the youngest player in 21 years to reach the  fourth round when he upset No. 5 Robin Soderling 6-1,  6-4, 7-5. On the ladies' side, No. 1 seed Caroline Wozniacki and Maria Sharapova advanced.

Serena Williams is trying for her third straight Wimbledon championship and fifth overall. Sister Venus already has five.

"I was more consistent,'' Serena said, "played my game more. Wasn't as tight
and nervous and uptight. I was able to relax more today.''

Asked if she had packed the big serve in her luggage (she had 14 aces), she

responded: "I was like, 'Where have you been?' He was at a party or something.  But he's back.''

Fish wasn't necessarily attending parties, but he had a reputation for not
training and suffered a series of injuries. They included spraining ligaments in  a foot in May 2007 when he tried to kick a field goal while visiting the Rhein Fire of the old NFL Europe. He is probably the only  person ever to withdraw from the French Open for that reason.

But two events were responsible for a change in his lifestyle. In 2008, he
married Stacey Gardner, one of the "Briefcase Models'' on the TV show "Deal or No Deal," and moved from Tampa to Beverly Hills.

Then in 2009, he had arthroscopic surgery on his left knee.

While  recuperating, the 6-2 Fish said he gave up carbohydrates and junk foods. He  reduced his weight from some 200 pounds to below 180 and said he began working  out with more intensity.

"We can all sit here and say we wish we would have done things differently,''
Fish said, "but I don't think about it at all. I'm excited to be playing the
best tennis of my life now.''

He won tournaments at Newport, R.I., and Atlanta last year and was a star of  the U.S. Davis Cup team in Colombia in September. He  made it to the third round of the French Open and now, after flying to California so he and his  wife could check on their pet dachshund and unwind, is the only U.S. male to get  out of the first week in Wimbledon singles.

His onetime tennis academy roommate, doubles partner and a former U.S. Open winner, Andy Roddick,  was eliminated Friday in the third round.

Fish isn't happy about being the only American man left. "It's lonely. It
doesn't feel great. And that's not the goal," Fish said. "You know, I want the
guys here. So that's a bit of a bummer, I guess.

"You know, you see a lot of guys . . . that sort of go downhill as they get
older. I'm going the other way. I have regrets in life. Nothing to do with
tennis. I sleep a lot better knowing now I'm doing everything I can to hit goals  I wanted to hit throughout my career.''

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