Ireland coach Joe Schmidt is awaiting fitness updates on scrum-halves Luke McGrath and John Cooney after both suffered injuries.
Ulster’s Cooney was a late withdrawal from Saturday’s European Champions Cup win over Racing 92, with his injury reported to be back related.
McGrath hobbled off in Leinster’s win over Toulouse with what the province stated was a “worrying leg injury”.
“Lukey has done something to his knee,” Leinster coach Leo Cullen later said.
The Leinster boss said McGrath had appeared to be in “some pain” and the injury would be assessed.
Ireland begin the defence of their Six Nations title against England in Dublin on 2 February.
Kieran Marmion, regular understudy to first-choice number nine Conor Murray in recent seasons, is out of action after undergoing ankle surgery following Ireland’s win over New Zealand in November.
At that stage, Connacht said Marmion would be unavailable until early February.
Lions star Murray only returned to Munster action in late November after being ruled out for five months by a neck injury.