Gethin Jenkins could face a race against time to be fit for Wales' RBS 6 Nations clash against Scotland at Murrayfield next week.
The Toulon prop suffered a calf muscle injury in last Saturday's 26-9 victory over Italy.
The 97 times-capped loosehead subsequently returned to his club, who have said they expect him to be sidelined for 10 days, but he was due back with Wales on Thursday for further assessment.
"We will find out a bit more when he arrives here and the physios can cast an eye over him," Wales assistant coach Robin McBryde said. "It is going to be a close call. We will have to see how he responds to treatment."
Bath prop Paul James would undoubtedly replace Jenkins if the 32-year-old is ruled out, with interim head coach Rob Howley due to announce the starting line-up next Tuesday.
Howley is also likely to look at the second-row, where a fit-again Alun-Wyn Jones could dislodge Andrew Coombs, while Sam Warburton will challenge strongly for a back-row recall.
"I think there will be a couple of selection issues," McBryde said. "As much as we benefited from keeping the same team (after France) for Italy, there were certain areas we are always looking to improve upon. We have got strength in depth to choose from, so I dare say there will be a few discussion points."
Coombs possibly missing out against Scotland would be tough on the Newport Gwent Dragons forward, given how much he has impressed in Wales' three Six Nations games so far during his debut international campaign.
But the all-Ospreys second-row pairing of Jones and Ian Evans is arguably Wales' strongest as they prepare to face Scotland and then England with a successful Six Nations title defence still possible.
"You never know how someone is going to react on their debut when given the opportunity, and I think Andrew has surprised everybody," McBryde said. "He has been very accurate in the work he has done. He rightly held on to his jersey for the last game. You are always looking to see where the next player in line is going to come from, and Andrew Coombs has shown there is more talent out there."