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Andy Roddick demonstrated why he is favourite to win Wimbledon by advancing to the fourth round with victory over Tommy Robredo.

Roddick defeated the highly-rated Robredo 7-6 6-4 6-4 and has yet to drop a set so far in the Championships.

The fifth seed was made to fight all the way in the first set and needed a tie-break to get the better of his young Spanish opponent on Centre Court.

The breaker was effectively decided by a Robredo double-fault and Roddick took it 7-5.

Roddick gained breaks in each of the next two sets, without ever dropping his own serve to comfortably progress to a last-16 meeting with Paradorn Srichaphan.

The Thai star was also a straight-sets winner on Friday, beating 17-year-old Spaniard Rafael Nadal.

Nadal began poorly and despite briefly threatening to hit back in the second set, he succumbed 6-4 6-4 6-2.

Roddick, who conceded he "probably should have lost" the first set, said there was a growing feeling that he could break his Grand Slam duck a week on Sunday.

"I'm starting to have a little bit more confidence in my abilities on a day-to-day basis.

"The first one's always the toughest to get. The biggest fear is the fear of the unknown. If you haven't done it before, you don't know yet.

"But I'm starting to believe in myself and I'm definitely here to try and win this tournament. The ultimate goal is to try to get a win.

"I'm playing good tennis at a Grand Slam and that's welcome. You take it when you can get it but you'd rather be playing your best tennis at a Grand Slam.

"I had good preparation, I feel good so far, so who knows?"

Elsewhere Swiss starlet Roger Federer eased into the fourth round at the expense of Mardy Fish late on Friday evening.

In a rain delayed match Federer, seeded four at SW19 this year, showed maturity beyond his years to dispose of his big-serving American opponent.

Federer took the first set 6-3 and looked to be cruising when he cantered to the next 6-1.

To his credit however Fish battled back and edged the third after Federer lost his serve with the scores at 4-4.

The crowd were firmly behind Fish by this stage but Federer remained calm as he played some sublime shots in the fourth to eventually close out 6-3 6-1 4-6 6-1 as the light began to fade.

Meanwhile, Sjeng Schalken looked in fine touch as he marched on.

The Dutch eighth seed had his serve in good working order as he swept aside lucky loser Victor Hanescu 6-2 6-4 7-6.

Schalken, who pushed eventual champion Lleyton Hewitt to five sets here in last year's quarter-finals, served seven aces and enjoyed an impressive first serve percentage of 69.

He dominated from the outset and the only chance the Romanian had came when the third set went into a tie-break.

However, Schalken was in no mood to stay on court any longer and took it 7-3 to book his place in the last 16.

There he will play ninth seed Rainer Schuettler who survived a nail-biting five-setter against veteran Todd Martin.

Martin rolled back the years to take a two-sets-to-one lead and looked on the verge of another Wimbledon victory.

But the two-time SW19 semi-finalist fell apart in the fourth set - which he lost 6-1 - and was then edged out in a tense final set.

Martin, now 32, broke back when the German served for the match at 5-4, but was unable to do so again two games later as Schuettler clinched a 4-6 7-5 6-7 6-1 7-5 win.

Lleyton Hewitt's conqueror Ivo Karlovic saw his fairytale run ended by Max Mirnyi.

Mirnyi - a relative dwarf at 6ft 5in - bludgeoned the 6ft 10in Croatian 7-6 3-6 6-3 7-6 to earn a fourth round place for the first time in his career.

In the women's singles, the big guns again had few problems.

Second seed Kim Clijsters was impressive once again, thrashing Samantha Reeves 6-1 6-2.

The Belgian has dropped just seven games so far this week and will now play Ai Sugiyama.

"I'm definitely improving with every game," Clijsters said. "I started well in my first match but today I think was even a little bit better.

"I think I served better again. I was really happy with the way I played today. Even when we had some tough rallies, I still felt like I was dominating and she couldn't really hurt me."

Former champion Venus Williams was just as impressive.

In what many thought would be a tough match, Williams romped to victory against Nadia Petrova, also winning 6-1 6-2.

Williams now faces her French Open conqueror Vera Zvonareva in the last 16.

The Russian teenager, who stunned Williams in Paris, was the first player into the last 16 after she beat Iroda Tulyaganova 6-3 7-5.

Williams was impressed with the way she played.

"I could look for a little extra pace on my strokes but I played well against a good player and it wasn't her fault she lost like that.

"I had another good day when I had all the right shots. When was the last time? Wednesday, I think."

Williams insisted she was over the slump that brought her the defeat by Zvonareva at Roland Garros.

Williams added: "I'm a professional and when I have a bad day I don't make excuses. I just try to come back stronger.

"In Paris it was definitely a fight against myself and although she (Zvonareva) hit some good balls at the end of the match I should have done better."

Another former champion, the 1999 winner Lindsay Davenport, demolished Cara Black 6-2 6-2 to join Williams and Clijsters in the last 16.

Davenport's serve was working well throughout and she restricted her opponent to just four winners in the match.

She now meets Shinobu Asagoe and stays on course for a quarter-final clash with Venus.

However, there was a shock late in the day when Chanda Rubin became the highest seed to fall in the women's singles.

In a rain-interrupted mach on Court One, the seventh seed went down 7-6 6-3 to Italian star Silvia Farina Elia.

Having won at Eastbourne in the run-up to the Championships, Rubin had been given an outside title chance by some but her hopes took a knock when she lost the first set on a tie-break.

A poor start to the breaker saw her fall 5-2 down and although she retrieved the situation, Farina Elia struck again to win it 8-6.

The only break in the second set came in the fourth game and although Rubin saved four match points she was unable to save herself from the exit door.

It is the first time that the 31-year-old Farina Elia has gone beyond the third round in 12 attempts in SW19.