WIMBLEDON, England -- Five-time champion Venus Williams needed three sets and nearly three hours to overcome the oldest player in the field Wednesday and reach the third round at Wimbledon.

With rain delaying play on the other courts at the All England Club, Williams outlasted Kimiko Date-Krumm 6-7 (6), 6-3, 8-6 in a compelling battle under the sliding roof of Centre Court that featured great shot-making from both players.

Williams relied on her big serve at key moments to overcome a gritty challenge from the 40-year-old Japanese player, who was the second oldest woman to reach the second round here in the Open era after Martina Navratilova.

"She doesn't play anywhere near her age," Williams said.

Following Williams on Centre Court was defending men's champion Rafael Nadal, who cruised past Ryan Sweeting 6-3, 6-2, 6-4 to move into the third round, showing just how tough he'll be to stop as he chases a third Wimbledon crown.

The top-ranked Spaniard, who beat the American for the third time this year, all in straight sets, had only seven unforced errors to go with his 38 winners. Nadal broke Sweeting five times and lost serve just once.

"I was playing very well," said Nadal, who finished in style on the last two points with a running backhand passing shot down the line and a forehand volley into the open court. "The second and beginning of the third I had the match completely under control, but he had a few good shots."

The opening contest ended with Date-Krumm hitting a backhand passing shot just wide to lose serve on match point after 2 hours, 56 minutes of play. Among those giving the players a standing ovation were all guests in the Royal Box, including Camilla, the Duchess of Cornwall and wife of Prince Charles.

Williams, who fell behind 5-1 in the first set before climbing back into the match, finished with 12 aces and 45 winners, one less than Date-Krumm. Williams had 24 unforced errors, while Date-Krumm had 31.

"It was tough. She came out and I just couldn't seem to get a game," Williams said. "She played so well and before I knew it the ball was past me every time in the first set."

It was the first time the two players -- who have a combined age of 71 -- have met in their long careers.

"She runs down every ball," Williams said. "She hits every ball basically on the baseline, hard and flat. If you get it anywhere near the midcourt, she hits for the corners and comes to the net.

"I thought she played unbelievable today. I thought she had some luck on her side, too, with net cords, balls hitting lines. I just thought today was a perfect storm for her to try to get a win. Thankfully I had some answers."

Williams, who turned 31 last week and is playing in her 15th straight Wimbledon, was pushed to the limit. Date-Krumm kept her off balance by ripping back her serves, hitting flat groundstrokes from corner to corner and sneaking into the net for drop volleys.

The 57th-ranked Date-Krumm made her Wimbledon debut in 1989, reached the semifinals in 1996 and retired later that year until her return in 2008.

"I played my tennis and (showed) I can fight with Venus also," Date-Krumm said. "She's a five-time champion here. She's a great player. So I can fight with her. It was a very, very good match for me."

With rain pounding on the translucent roof, Williams and Date-Krumm put on a fighting display of competitive tennis. The first set lasted 65 minutes, the third went 69 minutes. By comparison, Venus won her first match against Akgul Amanmuradova on Monday in 59 minutes.

"Obviously I'd prefer to win in straight sets with no breaks but against a player like her today, right until the end she was attacking," Williams said. "Even that last shot I thought I hit a great approach and she almost hit a passing shot, so that was the story of the match but I'm really glad I was able to serve well, I think that really got me through."

It was the third match played under the roof this week, with the tournament schedule already disrupted by rain. The roof was installed before the 2009 tournament and had been rarely used until this week. Matches eventually began after 3 p.m. on the outside courts Wednesday after the showers let up.

"It was awesome to be able to play," Williams said. "It was raining out there. It's definitely a little bit warmer and having not played on Centre Court without the roof I don't know if it was faster or not but it's fantastic that we have it."

The roof remained over Centre Court for Nadal's match, then was opened for Andy Roddick's match against Victor Hanescu.

"The Wimbledon Centre Court with the roof or without the roof, is probably the best court of the world," Nadal said. "It's always a pleasure playing in this court. For me today is a new experience."

Nadal's next opponent will be Gilles Muller, who advanced after big-serving Canadian Milos Raonic retired while leading 3-2 in the first set Wednesday. The 31st-seeded Raonic, who led the men's tour with 504 aces in 36 matches coming into Wimbledon, had been considered a threat on grass.

Among other top names scheduled to play Wednesday were Andy Murray and Juan Martin del Potro.

Among men advancing Wednesday were 2010 runner-up and sixth-seeded Tomas Berdych, who downed Julien Benneteau 6-1, 6-4, 6-2; No. 10 Mardy Fish, a 7-6 (6), 6-4, 6-4 winner over Denis Istomin; and No. 17 Richard Gasquet, who defeated Igor Kunitsyn 6-1, 6-4, 6-4.

Women's first-round winners included No. 13 Agnieszka Radwanska and No. 16 Julia Goerges.

Williams, who returned to tournament tennis last week at Eastbourne after a layoff of nearly five months with a hip injury, looked flat in the early going and fell behind 3-0 and 5-1 as Date-Krumm controlled the points.

But Williams settled into her game and ran off five straight games to go up 6-5, saving two set points at 5-3 and another at 5-4. Williams squandered a set point of her own at 6-5, then went down 6-2 in the tiebreaker and saved four more set points. At 6-all, Date-Krumm floated a forehand that just caught the outside of the line and finally converted on her eighth set point when Williams missed a backhand passing shot.

Williams broke twice to take the second set and went up a break at 2-0 in the third. But Date-Krumm wouldn't give in, breaking back for 2-1 when Williams double-faulted and then saving six break points in the fourth game.

"It's just important to play each point, and just to keep competing, keep battling," Williams said. "I feel like I'm playing better than Eastbourne. I feel like my movement is a lot better. I'm not feeling any pain from my injury right now so that's more than I expected."