Nadal battled back from being down two sets to one for the second straight match to defeat Philipp Petzschner, 6-4, 4-6, 6-7 (5-7), 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-set 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 because of tendinitis in his knees, called for the trainer four 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.’’

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 break point.

Murray will now face 18th-seeded American Sam Querrey, who overcame Belgian Xavier Malisse to reach the fourth round for the first time.

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 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.’’

The incident seemed to inspire Nadal, who closed 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.

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.’’

Also yesterday, 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 24th-ranked Thomaz Bellucci, 6-4, 6-2, 7-5.