|RBS Six Nations|
|Dates: 6 February-19 March|
|Coverage: Live coverage of eight games on BBC One and BBC One HD. All of Scotland's matches live on BBC Radio Scotland. Live text on BBC Sport website|
Centre Alex Dunbar and back rower Adam Ashe will both miss Scotland's opening two games of the Six Nations.
Dunbar, 25, suffered a posterior thigh strain during Glasgow's European Champions Cup win over Racing 92 and will be out "for the coming weeks".
Ashe, 22, requires further treatment on a shoulder injury and will also miss Scotland's matches against England on 6 February and Wales a week later.
Dunbar, who has 14 caps, was a likely starter against England if fit.
It is the latest setback to affect his Test career, after rupturing knee ligaments in training before last year's Calcutta Cup match and missing the World Cup last autumn as a result.
His Glasgow team-mate Mark Bennett is another injury concern, with Scotland coach Vern Cotter rating the outside centre's chances as no better than 50-50 as he recovers from a shoulder problem.
With Dunbar ruled out, Edinburgh's Matt Scott is likely to start at inside centre in the Calcutta Cup match a week on Saturday, with Saracens' Duncan Taylor in contention to join him in midfield.
Glasgow's Ashe, who has won six caps but missed the cut for the World Cup, can play at blind-side flanker or number eight and was one of seven back-rowers named in Scotland's Six Nations squad.
With Ryan Wilson omitted, Josh Strauss is the only other player in the squad with extensive experience of playing blind-side, although John Barclay has also operated there for Scarlets this season.
Head coach Vern Cotter may choose to start with two specialist open-sides against England, a tactic he employed against Australia in their World Cup quarter-final, when John Hardie and Blair Cowan both started.