Top-ranked Rafael Nadal has rallied for another five-set victory, overcoming knee problems, an umpire's warning and a tough challenge from a hard-hitting German to reach the fourth round of Wimbledon.
Nadal battled back from two-sets-to-one down for the second straight match to defeat Philipp Petzschner 6-4, 4-6, 6-7 (5), 6-2, 6-3 in a Centre Court slugfest.
Defending women's champion Serena Williams had a much easier time, serving 19 aces in a straight-sets win over Dominika Cibulkova that set up a fourth-round matchup with former champion Maria Sharapova.
The top-seeded Williams had at least two aces in each of her nine service games and overpowered the 46th-ranked Slovak 6-0, 7-5.
The second-seeded Nadal, who won the title in 2008 but missed last year's tournament due to tendinitis in his knees, called for the trainer four separate times for treatment on his left arm and right knee but never looked badly hurt.
"I hope I'll be fine," Nadal said afterward. "I don't know. I'm going to check. It's not a big problem. It's a long season for me. I have played a lot of matches the last few months.
"Having a five-set match two days ago and one today - that's tough. I'm happy to be in the fourth round. I'm going to try to be better for Monday."
Nadal said he will definitely play Monday's match against France's Paul-Henri Matthieu, who beat Thiemo de Bakker in four sets.
"I am here to try my best and to try to keep in the tournament," he said.
Nadal said his right knee has been bothering him for several months, and that he will skip Spain's Davis Cup quarterfinal against France next month in order to get treatment.
Fourth-seeded Andy Murray followed Nadal on Centre Court and beat Frenchman Gilles Simon 6-1, 6-4, 6-4, keeping alive Britain's hopes for a first homegrown male champion since 1936.
Murray, who hasn't dropped a set so far, served 15 aces, conceded only 15 points on serve and did not face a single break point.
Murray will now face 18th-seeded American Sam Querrey, who overcame Belgian Xavier Malisse to reach the fourth round here for the first time.
The 33rd-seeded Petzschner, playing his third straight five-setter, also needed medical treatment for a recurring hip problem on several changeovers and looked exhausted in the final set against Nadal.
The German questioned Nadal's injury breaks.
"You have to ask him what it was. But I didn't feel any difference afterwards or before. I thought he was moving great. I only could say if I would be injured like this once I would be happy. I don't know. Maybe he had something. Maybe it was just a clever part to take a time-out there."
Nadal denied any gamesmanship.
"I never call the physio when I don't have nothing, not one time in my career," he said. "If I call the physio today, it was because it was bothering me a lot, the knee."
Nadal received a warning from chair umpire Cedric Mourier at 2-2 in the fifth set for receiving coaching from coach and uncle Toni Nadal, who was sitting in the front row of the players' guest box. Rafael Nadal pointed angrily at the umpire, spread his arms wide and shouted at him before resuming play.
Nadal said he told the umpire he wants to discuss the issue later with the tournament supervisor.
"He wasn't giving me any tip," Nadal said. "He was only supporting me."
Toni Nadal denied coaching, saying he was only encouraging the player.
"I say, 'Positive! Positivo!' Nothing else," he said.
The incident seemed to inspire Nadal, who closed out the game with an overhead and looked over at his uncle with a sneer as he walked to his chair.
After a service hold by the German, Nadal ran off the last three games to finish the match. He got the decisive break to go up 5-2 when Petzschner missed a tired forehand wide. Nadal served out the match at love, then pumped his arms and saluted the crowd as he basked in a big ovation.
Nadal, who was stretched to five sets in the second round by Robin Haase, looked on the ropes for a while against the 26-year-old German. Petzschner served 25 aces and finished with 63 winners, compared to 56 for Nadal. But he also had 40 unforced errors, compared to 18 for the Spaniard.
Nadal faced only two break points and was broken just once, but went 1-11 on break points until converting his last three.
Williams, meanwhile, won 37 of 43 service points and held at love five times. She won 19 of her first 20 service points, with Cibulkova putting only four returns in play in that stretch.
"Serving that well feels awesome," Williams said. "I serve well at Wimbledon for some unknown reason. I want to keep doing it. I wish I could serve like this every tournament."
The first set lasted just 18 minutes, with Williams winning 25 of 31 points, serving six aces and hitting 12 winners. It was the third match in a row that Williams won the first set 6-0.
Cibulkova, a semifinalist at the French Open last year, finally got on the scoreboard when she held serve for 1-1 in the second set. From then on, she kept the match competitive by holding serve, although she couldn't cope with Williams' serves.
Williams credited Cibulkova with raising her game but was unhappy with her own performance in the second set.
"I just kind of came off the gas a little too much," she said. "Just can't do that in big Grand Slams like this."
Williams, chasing her fourth Wimbledon title and 13th Grand Slam crown, will face Sharapova on Monday in a rematch of the 2004 final won by the Russian.
Sharapova served an ace on match point to beat Czech player Barbora Zahlavova Strycova 7-5, 6-3. It was an uneven performance by Sharapova, who overcame 35 unforced errors and six double faults.
Sharapova is coming back into top form after right shoulder surgery in 2008. Because she is seeded 16th, she and Williams are meeting in the fourth round rather than the later stages.
"I definitely don't think it's early," Williams said. "It is what it is. You always have to be ready. She's obviously really good, especially on grass."
Recalling the 2004 final, Williams said, "I just remember I was really nervous. I think I put too much pressure on myself. It didn't work out. That was that."
Despite her easy run through the first three rounds this week, Williams said she didn't feel she is playing as well as last year when she beat sister Venus in the final.
"I definitely have to pick up and play better," she said.
Sharapova said she was looking forward to the showdown with Williams.
"I love playing against her," Sharapova said. "She's the defending champion. She's great on this surface. She's won numerous Grand Slams. If there's a challenge ahead of you, it's definitely playing against her, and I enjoy that."
Also Saturday, third-seeded Caroline Wozniacki made it to the fourth round by beating Anastasia Pavlyuchenkova 7-5, 6-4. She'll face unseeded Czech Petra Kvitova, who upset 14th-seeded Victoria Azarenka 7-5, 6-0.
In men's play, sixth-seeded Robin Soderling beat the 24th-ranked Thomaz Bellucci 6-4, 6-2, 7-5.
