SHIZUOKA , Japan (AP) — Ireland flyhalf Jonathan Sexton was available to play against Japan in the Rugby World Cup. Coach Joe Schmidt decided not to risk it.

Meanwhile, Japan brought back fit-again regular No. 8 Amanaki Lelei Mafi, and gave the captaincy to flanker Pieter Labuschagne while regular skipper Michael Leitch was dropped into the reserves.

Sexton, the 2018 world player of the year, received a bang to his quad against Scotland last Sunday and ceded goalkicking to scrumhalf Conor Murray. He was replaced with victory secured, didn't train fully this week, and missed out on selection on Thursday for the Japan game on Saturday.

Ireland gave a second start at 10 to Jack Carty in his first international season, and backed him with Joey Carbery, who has recovered from an ankle ligament injury sustained more than two months ago against Italy.

"Johnny's never happy about being left out, he's always looking to play, but he had a good hit-out against Scotland, played through 55 minutes and got a bit of mileage under his belt there," Schmidt said.

"We thought about his security off the bench but we also have a lot of time for Jack and wanted to get him involved as well. It just means we take the pressure off Johnny this week."

Carty helped Ireland finish off Scotland 27-3 in Yokohama, and was impressive.

"Jack's very calm, he doesn't get ruffled easily, he doesn't get distracted by an error he might make, or people trying to put pressure on him," Schmidt said. "So he stays in the zone very well."

Carty was one of four changes to the starting lineup, all of them in the backline.

Fullback Rob Kearney and wing Keith Earls shook off calf and thigh issues which prevented their availability against Scotland, and Chris Farrell was at inside center for Bundee Aki, who completed head injury assessments and was training fully, but not worth risking.

Flanker Peter O'Mahony failed a head injury assessment during the Scotland match but passed the concussion protocols afterwards and was picked in an unchanged forward pack. O'Mahony was to have sat out the match until Jack Conan hurt his foot in training when a teammate stood on it and he couldn't train fully.

"There's no elevated risk, we don't believe, in selecting Pete," Schmidt said. "And we've got a super medical staff."

Japan made six changes, two of them positional, to the starting side that beat Russia 30-10 on opening night.

Leitch, prop Asaeli Ai Valu, lock Wimpie van der Walt, and wing Lomano Lava Lemeki were dropped to the reserves.

Mafi was back after recovering from a shoulder injury against South Africa in the last World Cup warmup three weeks ago.

Prop Jiwon Koo, lock Luke Thompson — the oldest player in this World Cup at 38 — and fullback Ryohei Yamanaka come up from the reserves.

William Tupou was switched from fullback to wing for the first time in his test career, in place of Lemeki, and Kazuki Himeno was switched from No. 8 to flanker in place of Leitch.

Labuschagne, of South African heritage, becomes the third foreign-born player to captain Japan in a World Cup match.

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Lineups:

Japan: Ryohei Yamanaka, Kotaro Matsushima, Timothy Lafaele, Ryoto Nakamura, William Tupou, Yu Tamura, Yutaka Nagare; Amanaki Lelei Mafi, Pieter Labuschagne (captain), Kazuki Himeno, James Moore, Luke Thompson, Jiwon Koo, Shota Horie, Keita Inagaki. Reserves: Atsushi Sakate, Isileli Nakajima, Asaeli Ai Valu, Wimpie van der Walt, Michael Leitch, Fumiaki Tanaka, Rikiya Matsuda, Lomano Lava Lemeki.

Ireland: Rob Kearney, Keith Earls, Garry Ringrose, Chris Farrell, Jacob Stockdale, Jack Carty, Conor Murray; CJ Stander, Josh van der Flier, Peter O'Mahony, James Ryan, Iain Henderson, Tadhg Furlong, Rory Best (captain), Cian Healy. Reserves: Sean Cronin, Dave Kilcoyne, Andrew Porter, Tadhg Beirne, Rhys Ruddock, Luke McGrath, Joey Carbery, Jordan Larmour.

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