Japan captain Homare Sawa scored a hat trick as her side trounced Mexico 4-0 Friday to reach the quarter-finals of the Women's World Cup for the second time.

Sawa, playing in her fifth World Cup, opened the scoring in the 13th minute, and added her second in the 39th after Shinobu Ohno had made it 2-0 in the 15th.

The 32-year-old Sawa was in plenty of space when she was picked out by Yukari Kinga to complete her hat trick in the 80th, before 22,291 fans at the 29,870-capacity Bay Arena in Leverkusen. Germany.

"I didn't dare imagine that I would score three goals," said Sawa, who became her country's top scorer — male or female — with 78.

"I'm really, really surprised," she added. "I would like to continue to contribute as much as possible to Japanese football."

"Mentally and physically we will have to recover from this because this was quite painful, this defeat," said Mexico coach Leonardo Cuellar.

Japan pushed forward at pace when it had the ball and defended with commitment without it.

It was a frustrating afternoon for Mexico captain Maribel Dominguez. Early on, she was crowded off the ball, bringing an end to a promising move instigated by Stephany Mayor on the right wing.

Sawa deservedly put her side ahead shortly afterward, when she was allowed get to Aya Miyama's free kick to head past Cecilia Santiago from close range.

A clever touch that took the ball past two defenders allowed Ohno to fire high into the roof of the net two minutes later, after the alert Yuki Nagasato laid the ball off.

Japan's accurate passing and intelligent running off the ball meant Mexico was being completely overrun in midfield.

Santiago did just enough to put Kozue Ando off when the Japan forward was through on goal after a long ball forward in the 24th.

With half an hour played, fans began a series of Mexican waves, in a cruel twist for the beleaguered Mexicans on the field.

Dominguez found herself alone facing three Japanese defenders in the 33rd but her attempt was stopped, and although Veronica Perez was lucky to get another chance from the rebound, it was sent harmlessly wide.

Perez's free kick a minute later was easily gathered by Japan keeper Ayumi Kaihori.

Another header from Sawa — this time from a Miyama corner — effectively killed the game in the 39th.

Santiago should not have been beaten at the near post, but the competition's youngest ever goalkeeper — she was 16 years 251 days old for the draw with England — was left badly exposed by her weak defence.

In a rare instance of good fortune for the Mexicans, Nagasato had an effort wrongly ruled out for offside before the interval.

Mayor brought a smart save from Kaihori in the 49th, as Mexico sought a response, but still Japan pushed forward.

Nagasato's shot was deflected onto the post in the 56th, with Miyama hitting the crossbar from the resultant corner.

Cuellar appeared to wave the white flag when he took off the ineffective Dominguez for Kenti Robles — a defender — in the 62nd.

"The doctors were a little bit concerned about Maribel and we decided to take her off so she can play in the game against New Zealand," he explained. "She is a strong-willed player and she did what she could, but she's not at a 100 per cent."

His counterpart, meanwhile, warned against the rising expectations surrounding his side.

"It's an honour to be counted among the contenders for the final winner, but we need to go step by step," Norio Sasaki said.

"We are continuously improving. It's an ongoing process and we would like to get even better."