Captain Tyler Ardron, nursing a knee injury, will miss Canada's Rugby World Cup opener Saturday against Ireland.

Veteran forward Jamie Cudmore, in his fourth Rugby World Cup, will captain 18th-ranked Canada against No. 6 Ireland in Cardiff's Millennium Stadium.

Ardron has not played since injuring his medial collateral ligament July 29 against Samoa in Toronto in Pacific Nations Cup play.

"It's very close but it's just not worth the risk at this stage," Canadian coach Kieran Crowley said after announcing his lineup Thursday at a news conference in Swansea. "We want him for the rest of the tournament as well. He'll definitely be available for next week's selection but it's just come two or three days too early for him for this particular one."

Canada's next game is Sept. 26 against No. 14 Italy in Leeds, England.

The Canadians are kicking off the tournament with a bang. Ireland was ranked as high as No. 2 in the world at the end of August. Crowley, who was told there were only 500 tickets left at the 74,500-capacity stadium, calls it a massive challenge.

"They've selected a very strong team," he said of Ireland. "Probably close to their top team on paper, so they'll want to get their campaign off on the right foot.

"We've just got to go out there and look to have a good set platform and look to try and put our game on the field."

Sky Bet has Ireland as a 1-750 favourite to win, meaning a $100 bet will return 13 cents in profit. Canada is a 66-1 underdog, with a $100 bet returning you $6,700.

Fullback Harry Jones also misses out on the Ireland game, recovering from a shoulder injury suffered in a warmup game against Fiji.

"He is recovering OK. We expect him to be available for selection next week as well," Crowley said.

Matt Evans steps in for Jones, with Jeff Hassler and DTV van der Merwe on the wings and Nick Blevins and Ciaran Hearns at centre.

Nathan Hirayama opens at fly half with Gord McRorie at scrum half.

Former captain Aaron Carpenter fills in for Ardron at No. 8 with Kyle Gimour and sevens skipper John Moonlight at flanker. The 37-year-old Cudmore combines with Brett Beukeboom in the second row.

Props Hubert Buydens and Doug Wooldridge flank hooker Ray Barkwill.

In a somewhat surprising move, young lock Evan Olmstead does not make the matchday 23. Crowley had described the 24-year-old as the forward who had been the big mover in the leadup to the tournament.

Veteran Jebb Sinclair can provide cover for both the second row and back row. The London Irish forward starts on the bench, likely because he has seen limited action since recovering from a knee injury.

Van der Merwe and Carpenter are playing in their third World Cup.

Barkwill, Wooldridge, Beukeboom, Gilmour, Moonlight, McRorie, Blevins and Hassler are all making their tournament debut.

The Irish are defending Six Nations champions but enter the tournament on the heels of losses to Wales (16-10) and England (21-13).

Still Canada has never beaten Ireland, going 0-5-1 in matches between the two in all competitions.

Luke Fitzgerald comes in at centre for the injured Robbie Henshaw (hamstring) in an Irish team that has six World Cup debutantes. Scrum half Conor Murray has been deemed fit after suffering a concussion against England two weeks ago, while fullback Rob Kearney has recovered from a bruised knee.

The 20-team tournament opens Friday when host England, ranked fourth in the world, plays No. 9 Fiji at Twickenham.

Canada's roster

Hubert Buydens, Ray Barkwill, Doug Wooldridge, Brett Beukeboom, Jamie Cudmore (capt.), Kyle Gilmour, John Moonlight, Aaron Carpenter, Gordon McRorie, Nathan Hirayama, DTH van der Merwe, Nick Blevins, Ciaran Hearn, Jeff Hassler, Matt Evans.

Reserves: Benoit Piffero, Djustice Sears-Duru, Andrew Tiedemann, Jebb Sinclair, Richard Thorpe, Phil Mack, Liam Underwood.