Canada's all-time leading points scorer James Pritchard has come out of international retirement to replace the injured Liam Underwood at the Rugby World Cup.

Underwood's World Cup ended when he picked up a knee injury just 33 minutes after coming off the bench during the 50-7 defeat by Ireland, the latest injury blow for Canada after starting the tournament without captain Tyler Ardron.

Pritchard, 36, had announced his retirement just 35 days ago having missing out on a place in the original 31-man squad, but the Bedford fullback assured Canucks coach Kieran Crowley his services remained on offer throughout the tournament.

"It was a massive decision to leave him out," Crowley said of Pritchard. "James has been an outstanding servant to Canadian rugby, the highest points scorer.

"As I said to him at the time, the mix [of the squad] had gone past him, but be ready.

"He announced his retirement but he said if the opportunity came up in the World Cup, he was available, and he's obviously been training and playing with Bedford."

Pritchard scored a Canadian-best 607 points in 61 internationals since 2003, including 45 points in nine World Cup matches, but will have to wait for his appearance at a fourth World Cup after being left out of the match-day squad to face Pool D rivals Italy at Elland Road on Saturday. Matt Evans keeps his place at fullback, with Harry Jones on the bench.

"Now they might stop the 'Bring back Pritch' bandwagon that was going on," Crowley added, before dismissing suggestions that Pritchard's proximity to the tournament was the primary reason for his return: "If he'd been in Canada or Australia, if he's the next best, then he's in."

Ardron will return to the Canadian back row against Italy for his World Cup debut after recovering from his own knee injury.

"The knee is fine," the 24-year-old said. "I was pretty much ready to go against Ireland -- I've trained at 100 per cent for a few weeks now."