United States second rower Mark Cantoni will miss the World Cup after breaking an arm in the Tomahawks' shock 22-18 friendly victory over France in Toulouse.
The Australia-born forward, who qualifies for America through the grandparental rule, was in the US team that beat Jamaica to qualify for their first World Cup.
"Mark's been working for two years to get this opportunity so it's disappointing for him," said Tomahawks coach Terry Matterson.
"Hopefully we may be able to get him a run at the back end, that's how keen he is."
The loss of Cantoni has been offset by the arrival of former Hull KR forward Clint Newton, Wigan's new signing Eddy Pettybourne and former Castleford utility back Ryan McGoldrick, who all joined up with the American squad on their arrival in England.
"I've got a couple of selection headaches," said Matterson, whose side open their World Cup campaign against the Cook Islands in Bristol on Wednesday week.
Matterson is keen to play down the prospects of the tournament's 1,000/1 outsiders after they stunned the Catalan-dominated French in last Friday's warm-up fixture.
"It was a bit of a shock to the system for some of the guys playing at that level against guys that big, strong and fit but I think they showed they can handle that," he said.
"The challenge is to replicate that in a World Cup game."
