Scotland forwards Nathan Hines and Alasdair Strokosch have both been named in an initial 36-man squad to face Italy on Saturday week.
Leinster lock Hines missed last weekend's dramatic RBS Six Nations defeat in Wales with calf and ankle injuries, while Gloucester flanker Strokosch missed his country's opening two matches of the tournament with an ankle problem.
But both will be part of the enlarged party which will gather at Murrayfield on Sunday and train together on Monday and Tuesday, while additional players will be called up for Scotland A duty next week.
Scotland, who have lost their opening tournament matches, play Italy at the Stadio Flamini next Saturday, while Scotland A face Italy A in Biella the previous day.
Meanwhile, Scottish Rugby have confirmed Thom Evans had undergone a second neck operation at the University Hospital of Wales, Cardiff.
Scotland wing Evans suffered a serious injury after colliding with Wales' Lee Byrne at the Millennium Stadium on Saturday and had an operation that evening.
Team doctor James Robson, who has already ruled Evans out for the season, said: "Thom, after discussion with his family and the surgeons who performed his initial operation, elected to undergo a second procedure to enhance his recovery.
"This surgery has now taken place. Thom is in good spirits and the surgeons are delighted with his progress.
"Thom has asked me to pass on his heartfelt thanks to the thousands of people who have expressed their support.
"At this stage I would expect that, if Thom's recovery continues in the same vein, he will be able to return home next week."
Chris Paterson was set to return to Edinburgh from Cardiff on Friday after recovering sufficiently from the kidney injury that he suffered at the Millennium Stadium, where he was earning his 100th cap.
Dr Robson said of Paterson, who has been ruled out of the rest of the Six Nations:
"'Mossy' was discharged from hospital in Cardiff on Tuesday night.
"He has rested for a couple of days further in Cardiff and is now well enough to travel home with his wife Claire, which is excellent news.
Scotland head coach Andy Robinson visited both players in Cardiff and reported back: "It was uplifting to speak to both players and hear first-hand that they're both feeling better.
"Once again, on behalf of the Scotland team, I want to thank our own medical team, the Welsh Rugby Union medical personnel at the Millennium Stadium and all the staff at the University Hospital in Cardiff for the quite magnificent care they have delivered."