Japan head into the first test with Ireland showing five changes and one positional switch from the team that started last week's 33-21 win over Romania.

Head coach Jamie Joseph named his 23-man squad Thursday for Saturday's game at Shizuoka's Ecopa Stadium following a week that saw Harumichi Tatekawa, Akihito Yamada, Yu Chinen and 98-cap veteran Hitoshi Ono all pull out of the squad with injury.

In the backs, William Tupou wins his first cap and links up with Coca-Cola Red Sparks clubmate Timothy Lafaele (who moves from 13 to 12) in the centers. Yu Tamura gets the nod at flyhalf, while Kotaro Matsushima is named on the wing in place of Yamada.

"I thought (fullback) Ryuji Noguchi played well (against Romania) and wanted to give him another opportunity against strong opposition and see how he reacts under pressure," Joseph said, explaining why Matsushima was picked on the wing rather than in his favored No. 15 jersey.

"Matsu is another good player and we lost Aki with injury so it's good to have quality players who can play different positions."

There are two changes in the pack, with Keita Inagaki and Heiichiro Ito -- who both started last week's game on the bench -- packing down either side of captain Shota Horie in the front row.

On the bench, Shintaro Ishihara and Yutaka Nagare will get their first taste of playing a Tier 1 side, while Joseph has been forced to name two flankers among the replacement forwards, in Hendrik Tui and Shuhei Matsuhashi, as Japan's lack of depth in the second row is exposed.

Japan's win against Romania was marred by a less than impressive second half and Joseph said the team had worked hard in training during the week.

"Losing locks doesn't help our challenges but we are really pleased with our work this week. We've had a look at our maul defense where Romania got on top of us toward the middle stages of the game and put us under a lot of pressure."

Ireland are missing 11 players away with the British and Irish Lions in New Zealand and four senior players at home recovering from injury.

But coach Joe Schmidt has still named a powerful side that shows six changes -- five in the backs and one in the pack -- from the team that started last week's 55-19 win over the United States in New Jersey.

"Ireland are a strong team that put 50-odd points on a very committed USA side," Joseph said. "Their set piece is strong, both scrum and line-out, and a real threat to our game. But we know they are strong so our focus has been about playing our way and developing our game."

Blindside flanker Rhys Ruddock captains a team that contains a mix of young players with a handful of caps and experienced campaigners such as Simon Zebo, Keith Earls, Cian Healy and Devin Toner.

The side also contains two uncapped players on the bench in Kieran Treadwell and Rory O'Loughlin.

"Japan play very fast, are very skilful, use space very well and are difficult to contain if they get fast ball," Schmidt said Thursday after naming his team in Tokyo before they travel down to Shizuoka.

Both the coach and his players talked about Japan's 15-man approach to the game and said they expected a tough afternoon in the summer heat.

"Japan have threats all over the park and it's something we need to nullify if we want to get a result," said lock Quinn Roux.

The two teams, who have been pooled together in Pool A at Rugby World Cup 2019, have met five times in the past with Ireland winning all five, the last a 47-18 win in Tokyo in 2005.

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Japan squad: Keita Inagaki, Shota Horie, Heiichiro Ito, Kotaro Yatabe, Uwe Helu, Michael Leitch, Yoshitaka Tokunaga, Amanaki Lelei Mafi, Fumiaki Tanaka, Yu Tamura, Kenki Fukuoka, Timothy Lafaele, William Tupou, Kotaro Matsushima, Ryuji Noguchi.

Bench: Yusuke Niwai, Shintaro Ishihara, Takuma Asahara, Hendrik Tui, Shuhei Matsuhashi, Yutaka Nagare, Derek Carpenter, Rikiya Matsuda.

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Ireland squad: Cian Healy, Niall Scannell, John Ryan, Quinn Roux, Devin Toner, Rhys Ruddock, Dan Leavy, Jack Conan, Luke McGrath, Paddy Jackson, Keith Earls, Rory Scannell, Garry Ringrose, Andrew Conway, Simon Zebo.

Bench: James Tracy, Dave Kilcoyne, Finlay Bealham, Kieran Treadwell, Jack O'Donoghue, Kieran Marmion, Rory O'Loughlin, Tiernan O'Halloran.

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