Scotland out-halves Finn Russell and Adam Hastings have both been ruled out of the Autumn Nations Cup due to injury.
In a further setback, Glasgow Warriors playmaker Hastings is unlikely to feature at all during next year's Six Nations.
Racing 92 player Russell suffered a groin injury as he made his first start for Scotland in over a year during Saturday's win over Wales in Llanelli.
The 28-year-old was replaced by Hastings, 24, but he did not finish the 14-10 victory in the final game of this year's delayed Six Nations either after suffering a dislocated shoulder.
"Finn we hope will be back in time for the Six Nations, but it's unlikely Adam will be back before the end of that tournament," Scotland head coach Gregor Townsend told BBC Scotland.
"At the very best he'll come back at the end, but that will depend on how things go."
The Scots kick off their Autumn Nations Cup campaign away to Italy on 14 November before also taking on France and Fiji in the one-off eight-team tournament.
Skipper Stuart Hogg ended last weekend's victory - the Scots' first in the principality since 2002 - in the No 10 slot but the Exeter full-back has already admitted he would prefer to stay in the back-three, meaning Worcester's Duncan Weir could be handed a recall after his last start came against Ireland in March 2016.
Scotland open their Six Nations campaign away to England on 6 February.
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