Johnny Sexton has returned to training and head coach Joe Schmidt is confident the World Player of the Year will be fully fit to face England on Saturday week.
The 33-year-old Leinster fly-half has been inactive since picking up a knee injury against Munster last month.
Leinster head coach Leo Cullen said this week that Sexton was "not a million miles away" and speaking at the launch of the 2019 Guinness Six Nations today Schmidt said the 10 resumed light training today.
"He will train fully on Thursday," he said.
"Our expectation is that he will get through that without any problems at all."
Iain Henderson, who suffered a fresh setback during the Heineken Champions Cup victory at Leicester Tigers, "could potentially make the last two weekends, that will be quite tight".
The head coach said that Tadhg Beirne will "definitely" make the last two weekends after picking up a knee injury, and could possible return for the round three clash away to Italy.
"Tadhg has been so robust and resilient. He has played a lot of match minutes in the past three years. To pick up an injury is really disappointing for him."
Flanker Dan Leavy could be fit enough for the second game away to Scotland, with Schmidt admitting it will depend on whether he is involved in Friday night's Pro 14 clash as Leinster take on Scarlets.
"He'd inject a little bit of energy and intensity into that Scotland week potentially."
Rob Kearney and Jack McGrath have not travelled with the squad to Portugal in order to gain game-time in the Pro14 against Scarlets on Friday.