Flanker John Barclay will miss Scotland's tour of South Africa next month due to a shoulder injury, the Scottish Rugby Union (SRU) announced on Tuesday.
The 41-cap forward, who will join Welsh side Scarlets from Glasgow Warriors in the close season, is scheduled to undergo surgery later this week.
Scotland's interim head coach Scott Johnson, who is due to be replaced by Vern Cotter in 12 months' time, is not expected to replace 26-year-old Barclay in his 30-man squad.
In South Africa, Scotland are due to take part in a tournament involving the host nation, Samoa and Italy.
The SRU have also revealed that Scotland's first end-of-year international, against Japan on November 9, will be played at Murrayfield in Edinburgh.
Scotland will also face South Africa on November 17 and Australia on November 23, with both games due to take place at Murrayfield.