Prop Paul James is Wales' biggest fitness concern heading into a World Cup showdown against host nation England on Saturday.
The result of the match is likely to have a massive impact on the outcome of the Cup's `Pool of Death', with Australia, England and Wales all remaining undefeated and only two to progress.
James, who would be set for a bench role at Twickenham, suffered a tight calf muscle during last weekend's 54-9 victory over Uruguay, as did regular starting forward Samson Lee.
"Samson is further in front than Paul. We'll just have to wait and see," Wales assistant coach Rob Howley said.
"With our medical team we've got, we trust in them making that call. There are props on standby. We're waiting to make that call when we need to.
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"We have already contacted Rugby World Cup, and there is special dispensation for front rows which allows us to bring someone in even 24 hours before a game."
Fullback Liam Williams, looks set to line up on Saturday after taking a full part in training. He took a knock to his thigh during the Uruguay encounter.
Howley, meanwhile, has described Sam Burgess as "an imposing figure" ahead of the former rugby league star's expected elevation to World Cup starting duty on Saturday.
"Andy Farrell (England assistant coach) introduced me to him (Burgess) on the Lions tour in 2013," Howley said. "He's an imposing figure.
"I was impressed when he played with (Henry) Slade against France (last month). His ability to run hard lines and having that creative edge outside makes it more difficult defensively.
"It is important when playing against players like Sam to close down their space. It will be a challenge if Sam is playing at 12 at the weekend."
