Japan heads into Saturday's clash against Tonga knowing it will be more than a Pacific Nations Cup match, but a chance to test its 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, Osaka Prefecture, is perhaps the most crucial.

The 'Ikale Tahi, ranked No. 14 in the world, are a physical side, similar to their Pacific island neighbor, 16th-ranked Samoa, which Japan faces in its third pool A match on Oct. 5. Samoa beat visiting Tonga 25-17 in its 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 Saturday 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," Joseph 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 its line speed as well as brushing up its 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 its 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 its well-fought victory over Fiji that saw Japan score four of its five tries in the first half, he said the Brave Blossoms ran out of gas and were error-prone in the second half 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.

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 its time on 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 the Top League's Suntory Sungoliath.

"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."

Captain Michael Leitch, who started on the bench against Fiji as he returns from a groin injury, comes into the starting side at blindside flanker in place of Kazuki Himeno.

"We need to get (him) some game time," Joseph said of Leitch.

For Tonga, the test will be an opportunity to check the ground ahead of the World Cup as it plays two of its 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."