Ireland captain Johnny Sexton said on Tuesday he hopes to shake off a "niggle" and be back in training by the end of the week ahead of their opening Six Nations match with Wales on 7 February.
Flyhalf Sexton, 35, limped off during Leinster's PRO14 win over Munster last weekend and there was speculation it was a recurrence of a hamstring injury.
"Anytime you get a little niggle it is very frustrating. I trained very hard to make sure it did not happen ahead of a major tournament," he said at the competition's launch.
"Somewhat typically it did! I was in a good place before the Munster game but all I can hope for is to get back on the horse and train by the end of the week."
Sexton's battle with fitness issues has plagued him through his stellar career and he missed part of last year's Autumn Nations Cup due to injury.
However, he returned to mastermind the third place play-off win over Scotland and is hoping it proves a springboard for the Six Nations.
Sexton's men finished third in the annual tournament but were well beaten by both England and France.
The loss at les Bleus still rankles with Sexton, who was also criticised for his show of annoyance when head coach Andy Farrell took him off during the second-half.
"Last year we did not turn up against France. Hopefully we give them a better game in Dublin (14 February)," he said.
"I just want to get a couple of extra results (against France and England). Winning silverware is where you want to be at the end of the tournament," he added.
Sexton's provincial team-mate in British and Irish Lions prop Tadhg Furlong last played in February's loss to England due back and calf injuries.
Farrell, though, has included him in the squad and said he is making good progress.
"We will see how this week plays out whether Tadhg is physically and mentally right to be available for Wales," said Farrell.
"I have been speaking to him and he is feeling good and strong.
"Hopefully we can him get through to the end of the week and the plan would be all going well he is still in camp on Sunday has a full week of training and then assess him."
One player who is definitely out of the first two games is fullback Jacob Stockdale.
The 24-year-old was beginning to adapt well to the position at Test level after switching from the wing where he had been so devastating in the 2018 Grand Slam success.
"He is a top quality player and a guy who can make a difference," said Farrell.
"He is progressing well and it is nothing too serious. I understand that a bruise on the knee tends to take time to settle down.
"Hopefully he will be back up and running midway through the competition."