After days of fits and starts, Wimbledon built some momentum. It staged four fourth-round men’s singles matches simultaneously to start the day, and they swirled around a pair of intriguing women’s quarterfinals on Center Court.

Matches were spread around the All England Club and fans spent much of their time scanning the nearest scoreboard, constantly checking to see if an even better match was taking place elsewhere.

It left most of the seats empty at Center Court, where Venus Williams continued her assault on the top 10, a place she spent most of a decade residing and, at times, dominating. Less than 24 hours after dismantling No. 2 Maria Sharapova in two sets, she did the same to No. 5 Svetlana Kuznetsova, 6-3, 6-4, to glide into the semifinals.

After a shaky start to the tournament, Williams, seeded 23rd and ranked 31st in the world after a couple of injury plagued years, has rediscovered her groove. She will face Ana Ivanovic in the semifinals. Ivanovic, the sixth seed, fought off three match points and won the final four games against No. 10 Nicole Vaidisova for a 4-6, 6-2, 7-5 victory.

The top-seeded Justine Henin and No. 18 Marion Bartoli, the surprise survivor of the bracket, meet in the other semifinal, scheduled for Friday.

Thursday belonged mostly to the men’s half of the tournament, as Wimbledon officials tried to squeeze in all the necessary matches to keep the final slipping from Sunday into next week. It was the bottom half of the draw that was lagging, so four fourth-round matches were started at 11 a.m., an hour or two earlier than normal.

When they ended, Rafael Nadal, Tomas Berdych, Marcos Baghdatis and Novak Djokovic had moved on to the quarterfinals.

Nadal, the runner-up last year and the second seed this year, was relegated to Court No. 2, just another ring in the production.

His latest five-set victory, this one in come-from-behind fashion against Mikhail Youzhny, was simply part of the dizzying show — a sort of warm-up act to the main event, the long-awaited return of the four-time champion Roger Federer.

Federer had not played since last Friday, having sidestepped the raindrops that besieged the tournament in recent days. Six days after he last appeared, he walked back onto Center Court on Thursday afternoon to play a quarterfinal match with Juan Carlos Ferrero.

Nadal looked like he would not get to the next round. Youzhny, a 25-year-old Russian, started where he left off at last year’s U.S. Open, when he beat Nadal in the quarterfinals. Youzhny took the first two sets surprisingly easily, displaying the all-court wizardry and energy usually seen from Nadal. He punctuated big shots with flexed muscles and primal scream.

But Nadal, as if his batteries had been changed, roared back with a 6-1 victory in the third. Youzhny’s balky back acted up, and he spent the breaks during changeovers prone on the grass, being twisted by a trainer like a contortionist.

Fans provided spine-tingling cheers, alternately chanting for Youzhny and Nadal to add to the carnival atmosphere. Youzhny recaptured his form, but could not keep up with Nadal, who advanced with a 4-6, 3-6, 6-1, 6-2, 6-2.

“After the first two sets, the next three sets, maybe I played my best game on grass in my life,” Nadal said.

A reasonable question is just how much energy the 21-year-old sapped. His third-round match scheduled for last Saturday finally finished on Wednesday, and if he returns to the final, and if the final is on Sunday, he will have played five matches in five days.

“What can we do?” he said. “There is not another option. That’s it. Try the best every day.”

He will next play Berdych, the seventh seed, who beat Jonas Bjorkman, a semifinalist last year, in four sets on Court 18.

Another compelling men’s match unfolded between Djokovic and Lleyton Hewitt, the 16th-seeded Australian who won Wimbledon in 2002. Djokovic, ranked fifth in the world and the fourth seed here, won each of his three sets on tie breakers in the 7-6 (8), 7-6 (2), 4-6, 7-6 (5) victory.

Hewitt had a 5-4 lead in the fourth set, but lost two of the next three games to force another tiebreaker. He faced three match points, saved two of them, and then zipped a backhand into the net.

“I had my opportunity, and I couldn’t quite take it,” Hewitt said.

Hewitt beat Djokovic in straight sets at last year’s United States Open, but Djokovic has leapfrogged up the rankings since. Djokovic took off his shirt in celebration, then threw it into the Court 1 crowd.

It was a move that surely would have been welcomed at Court 13, on the club’s southern fringe. That was where Baghdatis, the 22-year-old Cypriot who made the semifinals last year, was cheered by his growing legion of raucous fans.

“The Greek Cypriots, we are a lot in the whole world,” Baghdatis said after his straight-set victory over sixth-seeded Nikolay Davydenko. “We have a lot in New York, in London. We’re 25,000 here. They came to see me, and that’s really nice.”

It gave even the far edges of Thursday’s action an appropriate circus-like atmosphere. After so much time spent in the rain during Wimbledon’s first nine days, there was something to celebrate.

And when the warm-up acts had done their job, igniting the fans and building anticipation for something even bigger, Federer arrived to a hero’s welcome.

He removed his sports coat and tailored pants, and played 38 minutes of tennis, his first in nearly a week.

Then it rained. The match was suspended in the first set, and Federer, finally, knew how everyone else felt.