Glasgow centre Peter Horne and Edinburgh scrum-half Sam Hidalgo-Clyne have been called into the Scotland training squad as "precautionary injury cover".
The news comes after Alex Dunbar and Chris Cusiter picked up injuries.
Glasgow wingers Tommy Seymour and Sean Maitland are also being monitored at Scotland's three-day training camp in Newcastle.
Both suffered head knocks in the win over Montpellier on Saturday.
Meanwhile, Edinburgh lock Grant Gilchrist, who was set to skipper Scotland in the autumn Tests, will have surgery later this week on the broken arm he suffered during his team's win over Lyon last Friday.
Flanker Hamish Watson has had surgery on a fractured jaw while fellow back row Roddy Grant will undergo surgery on Monday to correct a fractured bone in his cheek.