Japan head into Saturday's clash against Tonga knowing it will be more than a Pacific Nations Cup match, but a chance to test their strength and technique ahead of this autumn's Rugby World Cup.

Among the three tests remaining for Japan in the run-up to the sport's showpiece event, which opens on Sept. 20, the Brave Blossoms' match against Tonga at Hanazono Rugby Stadium in Higashiosaka is perhaps the most crucial.

(Japan rugby head coach Jamie Joseph watches his players train in Sakai, Osaka Prefecture, on July 31, 2019, ahead of the match against Tonga.)

The 'Ikale Tahi, ranked No. 14 in the world, are a physical side, similar to their Pacific island neighbors, 16th-ranked Samoa, whom Japan face in their third pool A match on Oct. 5. Samoa beat visiting Tonga 25-17 in their PNC opener last weekend in extremely muddy conditions at Apia Park.

The 11th-ranked Brave Blossoms hope to stage another confident victory following their 34-21 win over Fiji last week in Kamaishi, Iwate Prefecture. But head coach Jamie Joseph said he expects a difficult challenge from the Tongan team.

"They are very big men. Huge and powerful. So they will be very direct, I can imagine them trying to grab momentum by being very direct into our pack," he said.

"The Tongans will try to outmuscle us so we've got to watch that," he said, adding Japan will have to shut down Tonga's "time and space" with their line speed as well as brushing up their set-piece.

The two sides have played 17 times with Japan winning eight, including the most recent meeting, a 39-6 drubbing in France in November 2017.

Joseph did not say that he had picked his team or game plan with the World Cup clash against Samoa in mind, but the New Zealander said being able to adjust to their opponent and play for the entire 80 minutes is key even when fatigue and injuries are hindering the squad.

And while he praised his team for their well-fought victory over Fiji that saw Japan score four of their five tries in the first half, he said the Brave Blossoms ran out of gas and were error-prone in the second stanza at Kamaishi Recovery Memorial Stadium.

"We want to get more consistent with how we play the game," he said. "I felt like we were a lot better team against Fiji for 40 minutes but we were not ruthless enough. We need to be tougher there because other teams will come back and make us pay."

"We look to step it up this week. But the week has been a lot different to last week because (the players') bodies are tired and the boys all recover differently from a test match," Joseph said.

Kotaro Matsushima, who will once again start on the wing Saturday, indicated the team will adopt a game plan focusing on kicking the ball and taking their time in defense.

"They are such a physical side. How much they can play in this heat and humidity is an important factor," said Matsushima, who plays for Suntory Sungoliath in the Top League.

"We've been able to play under different game plans. I hope we can demonstrate the depth of our play -- that we can play both structured and unstructured rugby."

For Tonga, the test will be an opportunity to check the ground ahead of the World Cup as they will play two of their four pool matches at Hanazono.

"We want to put out a performance that is inspiring not only to the Tongan people but also to the Japanese people," Tonga coach Toutai Kefu said.

"Last time we played Japan, they beat us quite convincingly so you'd have to say they are the favorites after last week's performance. But we are improving every week."